Like other animals, we are          until we know it is safe to relax.

on purpose

on fire

on guard

on duty

考查介词短语辨析。句意：像其他动物一样，我们在知道安全的时候才放松警惕。A.on purpose 故意；B. on fire着火；C.on guard 警惕；D.on duty值班。结合后文we know it is safe to relax，可知我们在知道安全的时候才放松警惕。故选C项。

--- So you missed the meeting.

---           .I got there five minutes before it finished.

Not at all

Not exactly

Not especially

Not really

考查情景交际用语。句意：---你错过了开会。---我在会议结束前五分钟到达会场。可以看出答话者认为对方讲话不够确切。A. Not at all一点也不；不客气；B. Not exactly不确切   C.Not especially不是特别 D.Not really不是真的。故选B项。

The salesman scolded the girl caught         and let her off.

to have stolen

to be stealing

to steal

stealing

考查非谓语动词。句意：这个销售员责备了被抓住正在偷东西的女孩，然后，让她走了。分析句子结构，caught是过去分词作定语，修饰前面的名词 the girl,"女孩"和"偷东西"之间是主动关系，用现在分词作宾语补足语，构成catch sb doing sth结构。意为抓住某人正在做某事。故选D项。

---Let me help you cross the street.

---               ! I'm not that old.

Come on

No way

Take your time

Go ahead

考查情景交际。句意：---我来帮你过马路。---拜托。我还没有那么老。A. come on 可以表示鼓励，催促，加油，不耐烦等；B.No way 绝不；C. Take your time 别着急；D. Go ahead 表同意，继续。根据句意，选go ahead,可译为“拜托”。故选A项。

He          and wept when he heard the news.

took down

put down

turned down

broke down

考查动词短语辨析。句意：当他听到这个消息时，整个人都崩溃了并哭起来。A. took down  记下；B.put down记下；C.turned down调小，拒绝；D.broke down崩溃，坏掉。根据wept 可知此处应填"broke down"符合语境。故选D项。

It was along the Mississippi River _________ Mark Twain spent much of his childhood.

how

which

that

where

此处构成It was...that...强调句式，句中强调了介词短语along the Mississippi River。故选C。

Every evening after dinner, if not ________ from work, I will spend some time walking my dog.

being tired

tiring

tired

to be tired

考查省略句。当状语从句的主语和主句主语一致，且状语从句中有be动词的时候，可以把状语从句的主语和be动词一起省略，本题if后面省略了I am，句意：每天晚上吃完晚饭以后，如果不是很累，我就会花点时间来遛狗。故C正确。