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。

The sunlight is white and blinding,           hard-edged shadows on the ground.

throwing

being thrown

to throw

to be thrown

考查非谓语动词。句意：阳光炽白炫目，在地上投下浓重的阴影。主语The sunlight和throw是主动关系，因此要用现在分词表主动，此处是现在分词短语作状语。故选A项。

Small sailboats can easily turn over in the water ________.

if not managed carefully

if are not managed carefully

unless not managed carefully

unless are not managed carefully

The small car can't         a large family inside.

suit

press

collect

fit

考查动词词义辨析。句意：这辆小汽车装不下一大家子人。A.suit 相配，合身；B.press压；C.collect 收集；D. fit合适；容纳。suit表示尺寸和大小方面适合；此处表示小汽车容纳不下一大家子人。故选D项。

---Shall we have a talk with her tonight?

---There is no        talking to her. She will never listen.

good

value

point

worth

考查名词词义辨析。句意：---我们今晚要和她谈谈吗？ ---和她谈话没有意义，她不会听。A.good 好处  ； B.value 价值；C.point要点；D.worth价值。根据句意可知可知，此处是固定表达There  is no point (in) doing sth 做某事没有意义。故选C项。