Be able to
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Be able to
Be able to与can(或者过去时的could)含义相近:
I'm not able to move my leg = I can't move my leg. 我的腿动不了了。
然而，can主要表达一种随着时间流逝可以获得的能力或技能，而be able to更偏向于临时状况或者描述能力或没有能力:
He can't swim, he has never learned how.他不会游泳，他一直就没学会怎么游。
He's not able to swim, the swimming pool is closed today.他不能去游泳，因为今天游泳池关闭了。
He's not able to swim, the swimming pool is closed today.他不能去游泳，因为今天游泳池关闭了。
Be able to 也可以用来表达在过去和将来时态内的can:
I was able to get to the meeting on time, despite the fact that the metro was late. 即使发生了地铁晚点的这件事，我还是准时到达开会现场了。
You'll be able to use your arm by the end of the month. 这个月末的时候，你的胳膊就能用了。
练习 1
Icarus: Luckily, I avoid a traffic jam this morning when I came to work.
Polly: That is truly fascinating. I hardly wait to hear more. Unfortunately, I must go.
Polly: That is truly fascinating. I hardly wait to hear more. Unfortunately, I must go.
Icarus: Luckily, I was able to 1 avoid a traffic jam this morning when I came to work.
Polly: That is truly fascinating. I can 2 hardly wait to hear more. Unfortunately, I must go.
Polly: That is truly fascinating. I can 2 hardly wait to hear more. Unfortunately, I must go.
1 was able to: We use 'was able to' here because the verb in the second clause (came) is in the past tense. This is the best choice here.
1 can: We cannot use 'can' here because the verb in the second clause (came) is in the past tense, and 'can' cannot express past actions.
2 can: 'I can hardly wait' is a common idiom in English meaning 'I am impatient and eager'. Polly is using it sarcastically. This is the best choice here.
2 am able to: 'I am able to hardly wait' does not make sense.
练习 2
Choose the appropriate meaning for each phrase. (Be careful! each answer is used only once):
'Kevin isn't able to ride a skateboard' =
'Kevin shouldn't ride a skateboard' =
'Kevin can't ride a skateboard' =
'Kevin isn't able to ride a skateboard' =
'Kevin shouldn't ride a skateboard' =
'Kevin can't ride a skateboard' =
Choose the appropriate meaning for each phrase. (Be careful! each answer is used only once):
'Kevin isn't able to ride a skateboard' = Something is preventing Kevin from riding a skateboard. 1
'Kevin shouldn't ride a skateboard' = It would be better if Kevin did not ride a skateboard. 2
'Kevin can't ride a skateboard' = Kevin doesn't know how to ride a skateboard. 3
'Kevin isn't able to ride a skateboard' = Something is preventing Kevin from riding a skateboard. 1
'Kevin shouldn't ride a skateboard' = It would be better if Kevin did not ride a skateboard. 2
'Kevin can't ride a skateboard' = Kevin doesn't know how to ride a skateboard. 3
1 Something is preventing Kevin from riding a skateboard.: This is the best choice here. 'Isn't able to' is usually used when we wish to say that someone is 'prevented' from doing something or that something is 'impeding' someone from doing something. For example: I am unable to ride my bike today because the weather is awful.
1 It would be better if Kevin did not ride a skateboard.: 'Isn't able to' does not express the idea that it would be better if Kevin did not ride the skateboard.
1 Kevin doesn't know how to ride a skateboard.: 'Isn't able to' does not express the idea that Kevin 'doesn't know how' to ride the skateboard.
2 It would be better if Kevin did not ride a skateboard.: This is the best choice here. 'Should not' expresses that it would be better if Kevin did not ride the skateboard.
2 Kevin doesn't know how to ride a skateboard.: 'Shouldn't' does not express the idea that Kevin 'doesn't know how' to ride the skateboard.
2 Something is preventing Kevin from riding a skateboard.: 'Shouldn't' does not express the idea that Kevin 'is prevented' from riding the skateboard.
3 Kevin doesn't know how to ride a skateboard.: This is the best choice here. 'Cannot' is usually used when we wish to say that someone 'doesn't know how' to do something. Example: I can't swim, because I've never learnt how to swim.
3 Something is preventing Kevin from riding a skateboard.: 'Can't' does not express the idea that Kevin 'is prevented' from riding the skateboard.
3 It would be better if Kevin did not ride a skateboard.: 'Can't' does not express the idea that it 'would be better' if Kevin didn't ride the skateboard.
练习 3
In the sentences below, choose the verb which belongs in the blank: either 'be able to' or 'can'. Remember to use the correct tense!
I get to the show before they closed the doors, but my girlfriend had already left.
He take a long walk off a short pier for all I care.
Not many people believe me when I tell them I eat twenty-five hot dogs in less than an hour, but it's true.
Hopefully, Willy will leave the hospital soon.
This next question be about business if you'd like.
I get to the show before they closed the doors, but my girlfriend had already left.
He take a long walk off a short pier for all I care.
Not many people believe me when I tell them I eat twenty-five hot dogs in less than an hour, but it's true.
Hopefully, Willy will leave the hospital soon.
This next question be about business if you'd like.
In the sentences below, choose the verb which belongs in the blank: either 'be able to' or 'can'. Remember to use the correct tense!
I was able to 1 get to the show before they closed the doors, but my girlfriend had already left.
He can 2 take a long walk off a short pier for all I care.
Not many people believe me when I tell them I can 3 eat twenty-five hot dogs in less than an hour, but it's true.
Hopefully, Willy will be able to 4 leave the hospital soon.
This next question can 5 be about business if you'd like.
I was able to 1 get to the show before they closed the doors, but my girlfriend had already left.
He can 2 take a long walk off a short pier for all I care.
Not many people believe me when I tell them I can 3 eat twenty-five hot dogs in less than an hour, but it's true.
Hopefully, Willy will be able to 4 leave the hospital soon.
This next question can 5 be about business if you'd like.
1 was able to: We use 'was able to' here because the verb in the second clause (had left) is in the past tense. This is the best choice here.
1 can: We cannot use 'can' here because the verb in the second clause (had left) is in the past tense.
2 can: We use 'can' here because the speaker is expressing an indirect desire (not very nice one) that the subject of the sentence should walk off a pier. A 'pier' is a structure that goes from land out into a body of water, it is synonymous with a 'jetty'.
2 is able to: Although it may be grammatically correct to use 'is able to' here, it does not make sense.
3 can: We use 'can' here to show that the speaker 'is able to' eat so many hot dogs.
3 am able: We cannot use 'be able' here because it lacks the preposition 'to'.
4 be able to: We use 'be able to' here because it agrees with the auxiliary 'will'. This is the best choice here.
4 can: We cannot use 'can' here because it follows the future auxiliary 'will'.
5 can: We use 'can' here because it expresses the possibility that the next question 'can be' about business. This is the best choice here.
5 is able to: We cannot use 'is able to' here because this construction does not express capacity or ability. We are trying to express the possibility that the question's subject can be about business.
练习 4
Jeremiah had a lot of trouble studying for his test last night. He concentrate because the alien spaceships were finally landing in his neighborhood. It probably doesn't matter. Once the aliens take over the planet, the history of the French Fifth Republic won't be very important. He had always wanted to study lasers, but his parents said he was an idiot. 'What you do with lasers?' they would ask him. 'Well, I'll defend myself against the alien invaders,' he said. Then his parents just laughed. But they're not laughing any more. The aliens have turned them into mashed potatoes.
Jeremiah had a lot of trouble studying for his test last night. He couldn't 1 concentrate because the alien spaceships were finally landing in his neighborhood. It probably doesn't matter. Once the aliens take over the planet, the history of the French Fifth Republic won't be very important. He had always wanted to study lasers, but his parents said he was an idiot. 'What can 2 you do with lasers?' they would ask him. 'Well, I'll be able to 3 defend myself against the alien invaders,' he said. Then his parents just laughed. But they're not laughing any more. The aliens have turned them into mashed potatoes.
1 couldn't: This is the best choice here. 'Could' is often used as the preterit form of the verb 'to be able to' or 'can'. We know that we need to use the past tense here because we are talking about 'last night'.
1 can't: We cannot use 'can' in the past tense.
1 shouldn't: 'Shouldn't' doesn't make sense here. 'Should' is typically used as a suggestion or a warning. For example: 'You shouldn't study history if you want to kill aliens'.
1 isn't able to: We cannot use 'is able to' in the past tense.
2 can: This is the best choice. Because the question is asked in the present tense, and in the affirmative form, we use 'can' here.
2 are able to: 'What are able to you do?' is grammatically incorrect. We would have to say: 'What are you able to do?'.
2 should: 'Should' doesn't make sense here. 'Should' is typically used as a suggestion or a warning. For example: 'You shouldn't play with lasers, you could get hurt'.
2 may: 'May' does not make sense here. 'May' is typically used as a form of politeness.
3 be able to: This is the best choice here. Because we are using the future construction 'I will', we have to use 'be able to' instead of 'can'.
3 can: 'Can' cannot be used in future tense constructions.
3 could: 'Could' cannot be used in future tense constructions. 'Could' is the preterit form of 'can'.
3 may: 'May' cannot be used in future tense constructions. Often, however, 'may' already carries a sense of future.
练习 5
Luna: Hi, Horatio. I ask you a question?
Horatio: No.
Luna: Great! I was wondering if you able to fix my chair yet?
Horatio: No.
Luna: That's ok. you want to drink some tea with me?
Horatio: No.
Horatio: No.
Luna: Great! I was wondering if you able to fix my chair yet?
Horatio: No.
Luna: That's ok. you want to drink some tea with me?
Horatio: No.
Luna: Hi, Horatio. Can 1 I ask you a question?
Horatio: No.
Luna: Great! I was wondering if you were 2 able to fix my chair yet?
Horatio: No.
Luna: That's ok. Do 3 you want to drink some tea with me?
Horatio: No.
Horatio: No.
Luna: Great! I was wondering if you were 2 able to fix my chair yet?
Horatio: No.
Luna: That's ok. Do 3 you want to drink some tea with me?
Horatio: No.
1 Can: This is the best choice here. 'Can I ask you a question?' is a proper interrogative form which asks for permission to pose a question. Note: 'May I ask a question' expresses the same meaning more politely and more accurately, but 'Can I ask you a question?' is acceptable and very common.
1 Am I able to: This is incorrect. Luna is not questioning her capacity to ask a question, but she is simply asking for permission to pose it.
1 Should: This is incorrect. In the interrogative form, 'should' is used to ask for advice or someone's opinion. If Luna were to ask 'should I ask you a question?' she would be asking herself if it is good idea to ask this question, which is very unlikely.
2 were: We use the past tense form 'were able to' because of the presence of 'yet' at the end of the phrase. 'Yet' tells us that Luna is asking about whether Horatio made an attempt to fix her chair in the past.
2 are: We cannot use the present tense form of the verb 'to be able' here because of the presence of 'yet' at the end of the sentence, which indicates that this event took place in the past.
2 was: We cannot use 'was able to' here because Luna is addressing Horatio directly, in the second person form. In the conditional tense, we must use 'were able' in this construction.
2 is: We cannot use the present tense form of the verb 'to be able' here because of the presence of 'yet' at the end of the sentence, which indicates that this event took place in the past. Also, 'is able' is the third person form of the verb, and Luna addressing Horatio in the second person (you).
3 Do: This is the best choice here. When asking a question about desire (with the verb 'to want') we use the auxiliary 'do' to pose the question correctly. Note that the verb which follows 'want' is put in the infinitive form (Do you want TO DRINK some tea with me?).
3 Are: We cannot use 'are' to ask this question. 'Are' is a form of the verb 'to be', which has no place in this construction, because this question is about Horatio's desire to drink tea with Luna.
3 Can: The construction 'can you want...' is grammatically incorrect. In the interrogative form, 'can' is used to ask for permission or capacity, never desire.
3 Could: Although this choice is grammatically correct, it is very unlikely that Luna would ask 'Could you want to drink some tea'. This construction would express that Luna was asking IF there was a possibility that Horatio would want to drink some tea with her. This is complicated conditional construction which is illogical and needlessly existential.
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