题目内容：

With their furry round heads and big black eyes, Zhongzhong and Huahua look just the same as any other monkey. But they happen to be the world’s first cloned (克隆的) monkeys.

Years ago, scientists used cloning techniques to produce Dolly, the world’s first cloned mammal (哺乳动物).They now used the same technique to produce the monkeys in China.

In animal cloning, animals are produced in a lab by using DNA that is taken from the cells (细胞) of a naturally-born animal. To clone Zhongzhong and Huahua, scientists from the Chinese Academy of Sciences (CAS.中国科学院) first removed the nucleus (细胞核) from a monkey’s egg cell (卵细胞). They then put another nucleus taken from the monkey’s body cells into the egg cell. The newly-formed egg was put into the womb (子宫) of a female monkey. Finally, Zhongzhong and Huahua were born.

The cloning process is hard, especially removing nucleus. It needs to be done in a fast and precise (精确的) way. The faster you do it, the less damage is done to the egg, according to CAS. Scientist Liu Zhen spent three years practicing removing the nucleus.

Unlike common monkeys, cloned monkeys have the same DNA as each other. When doing experiments on them, scientists can easily know that certain results are caused by different treatments, rather than different genes.

According to Sun Qiang from CAS, most drug trials (药物试验) are done on lab mice. However, drugs that work on mice might not work on humans. The two species are very different.

“Monkeys and humans are much closely related and testing on monkeys is supposed to be as effective (有效的) as testing on humans,” Sun added.

1.Zhongzhong and Huahua are ______.

A. naturally-born monkeys

B. the world’s first cloned mammals

C. the world’s first cloned monkeys

D. twin sheep that were born by Dolly

2.What do we know about the two monkeys?

A. They look different from other monkeys.

B. They have the same DNA.

C. Their body cells don’t have any nucleus.

D. They can live for only three years.

3.What can we learn from Paragraph 4?

A. Removing the nucleus is difficult.

B. The cloning process is very safe.

C. It took three years to remove the nucleus.

D. It is impossible to clone other animals.

4.Why do scientists want to do drug tests on monkeys?

A. Because it’s easier to use them for tests.

B. Because there are not enough mice.

C. Because drugs work well on monkeys.

D. Because monkeys are similar to humans.