阅读理解。

     Koalas are found only in Australia. Even if called koala bear, this animal has nothing to do with the actual

bear; it is not even a mammal (哺乳动物), but a marsupial (有袋动物), like the kangaroo. Its closest living

relatives are the wombats (毛鼻袋熊). A koala is about 60-80cm long and weighs 5-14kg. 

     The name "koala" means "no drink", and refers to the koala's ability to go for days without water. Koalas

get the water content they need from the eucalyptus (桉树) leaves on which they feed. The koala is the only

mammal with a digestive system that can feed only on eucalyptus leaves-incidentally, these leaves are highly

poisonous if eaten by humans. One individual consumes about 5kg of eucalyptus leaves daily and it may never

drink water!

     The koala is a nocturnal mammal. They prefer to move around just after sunset, spending daytime sleeping

in the form of a tree. A koala spends sleeping 75% of its time. The eucalyptus leaves they eat are rich in fiber

and poor in proteins and fats. The adult must detoxify (排毒) leaves with energy expense, while fiber is hard

to break down. Because of this poor diet, koalas save energy by sleeping most of the day, while their

movements are very slow.

     Koalas only have one young per year. In summer, baby koalas are born about a month after mating. The

female takes it with her mouth and places it into her poach. In 6 months, the young can get out and feed on

leaves. There are probably around 2,000 to 8,000 wild koalas in Australia at present. The extremely fine gray

fur is the reason why koala has been heavily hunted in the past. Koalas are killed every year by dogs, cats,

dingoes, eagles and owls. They also die of disease and accidents.

1. Koalas do not get poisoned when eating eucalyptus simply because of their _____.

A. special need

B. living habitat

C. digestive system

D. born laziness

2. Why does the koala spend most of its time sleeping?

A. To escape from natural enemies.

B. To save its energy.

C. To protect itself from the sun.

D. To detoxify eucalyptus leaves.

3. The underlined word "nocturnal" in the passage refers to "_____".

A. active during the night

B. excited in the daytime

C. inactive during the night

D. upset in the daytime

4. What information will probably be provided following the last paragraph?

A. Steps to protect the koala.

B. Living areas of the koala.

C. Ways the female feeds her young.

D. The decreasing number of the koala.