Drugs come in different forms．However，can you imagine that drugs come in chicken eggs？A team of scientists from England prove that it can come true．They have developed special chickens that lay eggs with drugs inside．These special drugs can help treat some kinds of diseases．Until now，they have made two kinds of drugs．One drug can treat skin cancer and the other can treat a nerve disease （神经性疾病）．

Certain drugs are produced by the special chickens inside their egg whites．These drugs are made of proteins（蛋白质） which can be found in animals'skin，hair，milk and meat．The scientists also use DNA technology to make sure that the drugs are only inside the egg whites．In this way，the chickens can stay healthy．

Besides egg whites，drugs made of proteins come in milk of cows and sheep．Compared with cows and sheep，the special chickens have ascendancyover them．First，they are cheaper to raise．Second，they need less room and grow faster．

These special chicken can pass on their drug﹣producing ability to their children．So far，five generations （代） of the special chickens have appeared．But scientists may need more time to make the drugs perfect．It's said that scientists will realize their dream in five to ten years．

根据短文内容选择最佳答案．

46．The underlined word" ascendancy"in the passage means" 　　"in Chinese．

A．

情况

B．

优势

C．

劣势

47．According to the passage，the special drugs are 　　．

A．

pills that can treat all cancers

B．

just the scientists'imagination

C．

made of proteins

48．According to the passage，the special chickens 　　．

A．	need less room and grow faster
B．	were developed by scientists from France
C．	produce certain drugs outside the eggs

49．Which of the following is TRUE according to the passage？ 　　

A．	The scientists never use DNA technology to keep the special chickens healthy．
B．	It may take scientists more time to make the drugs perfect．
C．	Until now，scientists have made three kinds of drugs．

50．What is the passage mainly about？ 　　

A．	It's mainly about a serious disease．
B．	It's mainly about a natural ability of the special chickens．
C．	It's mainly about the special drugs．