87．

He knew France well, as if he had been there many times.

(似乎他多次去过那个国家)

88.

Seeing those pictures, the student couldn't help thinking of those memorable days. (回忆起那些难忘的日子)

89.

Only after they had performed hundreds of experiments, did they succeed in solving the problem. (他们才成功地解决了这个问题)

90.

Some people hold the mistaken belief that our domestic products

are always inferior to imported goods. (总是次于进口商品)

来源：文都教育

91. sometimes giving up is helpful for you to concentrate time and energ on(有助于你把时间和精力集中于) a few things that are truly important.