12．People have planted a great many trees in order to________wind and sand in the desert.

A．hold down B．hold up

C．hold back D．hold out

13．-Thank you for your timely help，Susan.

-________.

A．With pleasure B．My pleasure

C．All right D．No thanks at all

14．-What did he come here for?

-He came here especially to________your acquaintance.

A．take B．get

C．make D．produce

15．On hearing the horrible noise，they all went out and looked at what was happening in________.

A．amusement B．enjoyment

C．amazement D．embarrassment

Ⅱ.阅读理解

The zebra belongs to the horse family. One of nature's great mysteries is why the zebra has stripes. One theory is that the stripes help the zebra cool down. On hot days the black stripes get a lot hotter than the white area of the zebra and under the black stripes there are special layers of fat for protection. Hot air then rises off the black stripes，forcing colder air down around the white areas，cooling the zebra down. This，however，is just a theory. The stripes can also confuse predators (食肉动物) when zebras stay with other animals in great numbers.

Zebras have excellent hearing and eyesight and can run at a speed of up to 35 miles per hour (56 kilometers per hour)．They also have a powerful kick that can cause serious injury to a predator，like a lion，or an African wild dog. Usually the lead male of the herd stays at the back of the group to defend against predators if necessary，while the females and youngsters run from danger.

Zebras are herbivores and feed mostly on grasses，although they also might eat the leaves and stems (茎) of bushes a bit. They eat grasses for many hours each day，using their strong teeth. Spending so much time chewing wears the zebra's teeth down，so their teeth keep growing all their lives. As the dry season arrives and the grasses die back，zebra herds travel to find more food and water holes for drinking. Most zebras have no specific territories. They travel from place to place，never staying in one area very long.

1．What can be inferred from the first paragraph?

A．There are different opinions about why the zebra has stripes.

B．The black stripes help the zebra live through cold days.

C．The zebra can easily be attacked by predators.

D．The zebra always travels with other animals.

2．According to the passage，herbivores are________.

A．animals that have specific territories

B．animals that only eat plants