2 . They often cover only their eyes with their hands, leaving the rest of their bodies   ________ (expose). (所给词的适当形式填空)

3 . 除非被邀请讲话，否则你在会上应保持沉默。(状语从句的省略)
________________, you should remain silent at the conference.

4 . Though not known to use tools in the wild, the birds have proved skillful at tool use while ________ (keep) in the cage.(所给词的适当形式填空)

5 . _______(occupy) with all sorts of affairs, the manager had little time to have a good sleep. (所给词的适当形式填空)

6 . Applications should be ______ (提交) as early as possible. （根据汉语提示单词拼写）

7 . The professor entered the hall, ________ (follow) by a group of students. (所给词的适当形式填空)

8 . In certain licensed zoos, animal experts will make sure that the koalas ___________ (select) for each session are in a good state for human contact. (所给词的适当形式填空)

9 . When he came to himself, he found himself __________ (被锁在) in the room. (根据汉语提示单词拼写)

10 . He was doing his homework one Sunday morning when he smelt something ________.

A．burnt

B．to be burnt

C．having been burnt

D．to burn