Use of be able to

1] The law cannot become the guardian of our private manners. (Use- Be unable to)
2] I couldn’t pay the fare. (Use- Be able to)
3] We cannot get them back by invoking the law. (Use- Be able to)
4] He could not rest till he left it behind a couple of hundred miles. (Use- Be unable to)
5] But no legal system could attempt to legislate against bad manners. (Use- Be able to)
6] Wordsworth was able to gather lessons of wisdom. (Remove -Be able to)
7] How can you be otherwise with Saturn where he is? (Use- Be able to)
8] If only he could reach a table in the restaurant unsuspected, success would be his. (Remove - could)
9] The king is able to do nothing wrong. (Remove - Be able to)
10] She was able to face the whole horror. (Remove - Be able to)
11] she could not be fashionable. (Remove - Be able to)
12] You can’t get out of it now. (Use - Be able to)
13] Now she could see flies crawling slowly out of a saucer of milk with their wings stuck together. (Use - Be able to)
14]I  can  buy  some  jaggery  and  coconut tomorrow. (Use - Be able to)
15] can imagine that lift-man, (Use - Be able to)
16] he can have the service for asking(Use - Be able to)
17] It cannot be too widely diffused (spread) in a rather drab (gloomy) world. (Use - Be able to)
18] We cannot get them back by invoking  the law. (Use - Be able to)
19] you can also track the condition of the goods. (Use - Be able to)
20] Why can’t we produce good toys in India?  (Use - Be able to)

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