let能否用于被动语态
 【问】 高中英语课本第一册有这样一道练习题：She didn’t let Jack go out.该书教参(P.73)给的答案是：Jack wasn’t let to go out.请问动词let可用于被动语态吗?
 【答】 CGEL (§16 .52)在讲述“宾语+不带to的不定式补足语”这一动词类型时，把let与have，make归在一类，并特别注明make可用于被动语态，而let和have则不能。
 They made him understand. [原书缺损]
 3. The explosion is liable to occur at any time.
 爆炸可能随时发生。
 B. to为介词，后跟名词或名词短语，其词义为：“容易受”、“容易患”：
 1. He is liable to heart trouble.
 他易发心脏病。
 2. Iron is liable to rust.
 铁容易生锈。
 be liable for表示“(在法律上)对……负责”：
 1. The child is only ten years old： his parents are liable for his behavior.
 这个孩子刚刚十岁，因此他的父母应对他的行为负法律责任。
 2. They are liable for his debts.
 他们对他的债务负法律责任。
 请做下面的英语试题：
 1. The driver of the car was liable for the damages caused to the passenger.A. arrested B. liberated C. legally responsible D. proposed.
 2. This road is_____to flood in winter.
 A. leading B. unprotected C. conductive D. liable
 3. If you drive a motorcar to the danger of the public，you may make yourself liable to aheavy fine.
 A. subject to B. acquainted with C. alert to D. relevant to