Can, Could, 和 Be Able To 练习题详解
以下是每道题目的详细解析，包括正确答案和原因，帮助你深入理解 can、could 和 be able to 的用法。
一. 单项选择题解析
Which sentence is correct?
答案：B. I can swim.
解析：
A错误：can 后面接动词原形，不需要加 to。
C错误：can 本身是一个情态动词，不需要再用 be。
D错误：can 后不能接 -ing 形式。
My grandmother ______ read when she was six years old.
答案：B. could
解析：
句子提到的是“过去”的能力，用 could 表示过去的能力最合适。
They ______ finish the project on time because of the bad weather.
答案：D. All of the above
解析：
can’t、couldn’t 和 weren’t able to 都可以表达因天气原因无法完成任务：
can’t：当前任务无法完成。
couldn’t：过去的某一次尝试失败。
weren’t able to：过去的能力或尝试失败，语意与 couldn’t 类似。
After she graduates, she ______ get a better job.
答案：C. will be able to
解析：
句子指“毕业后”的未来能力，使用 will be able to 来表达未来的可能性或能力。
I’m sorry, but I ______ help you move this weekend.
答案：D. Both A and C
解析：
can’t 用于口语中，表示“无法帮忙”，语气更直接。
won’t be able to 更正式，明确表示“将来”无法帮忙。
______ you open the window, please?
答案：B. Could
解析：
Could 比 can 更礼貌，用于正式请求。Will 和 should 在此语境不常用。
By the time he was five years old, he ______ already write his name.
答案：A. could
解析：
By the time... 表示过去某一时点之前的能力，使用 could 最为合适。
They ______ see the mountain clearly through the fog yesterday.
答案：D. Both B and C
解析：
could：表示过去的一般能力。
were able to：表示在特定场合下成功完成某件事情。
二. 填空题解析
My sister ______ (can, negative) swim until she was 12 years old.
答案：couldn’t
解析：
描述“过去”的能力，否定用 couldn’t。
We ______ (be able to) clean the house before the guests arrived.
答案：were able to
解析：
用 be able to 表示过去某次尝试取得成功。
In the future, I ______ (would like to, be able to) travel around the world.
答案：would like to be able to
解析：
would like to 表示愿望，后面跟 be able to 强调想要具备的能力。
Sorry, but I ______ (not, be able to) join the meeting tomorrow.
答案：won’t be able to
解析：
指“将来”无法参加会议，使用否定形式 won’t be able to。
三. 改错题解析
I can be able to solve this problem.
正确答案：I can solve this problem. / I am able to solve this problem.
解析：
can 和 be able to 不能同时使用。选择其中一个即可。
Could you to help me with this box?
正确答案：Could you help me with this box?
解析：
情态动词 could 后直接接动词原形，不需要加 to。
She won’t can attend the event next week.
正确答案：She won’t be able to attend the event next week.
解析：
can 不用于将来时，应该用 will be able to。
四. 连词成句解析
(can / play / the piano / he)
正确答案：He can play the piano.
解析：
按陈述句语序，主语 He 后接情态动词 can 和动词原形 play。
(I / couldn’t / when / ten / ride a bike / was)
正确答案：I couldn’t ride a bike when I was ten.
解析：
按过去时语序，couldn’t 表示能力的否定，时间状语放在句尾。
(be able to / we / the package / find / were / at last)
正确答案：We were able to find the package at last.
解析：
使用过去式 were able to 表示过去一次性成功的事件。
(will / after / speak French / she / able to / be / learning for two years)
正确答案：She will be able to speak French after learning for two years.
解析：
未来能力用 will be able to 表示，学习两年后获得能力。
五. 综合应用题解析
短文填空
正确答案：
By the time I was seven years old, I could read books in both English and Spanish. However, I couldn’t write in Spanish very well at that age. My parents helped me a lot, so by the time I was ten, I was able to write short essays in both languages. In the future, I would like to be able to write a book about my experiences learning languages.
解析：
could：过去的能力。
couldn’t：过去能力的否定。
was able to：特定事件中的成功。
would like to be able to：对未来能力的期待。
学习总结
通过这套题目和解析，你可以清楚地看出：
Can 用于现在和一般能力。
Could 表示过去的能力，也可用于礼貌请求。
Be able to 可用于所有时态，并特别用于特定场合的能力或成功。
