51．The writer holds that the potential to make healthy body tissues will＿＿＿．
　　[A]aggravate moral issues of human clohing
　　[B]bring great benefits to human beings
　　[C]help scientists decode body instructions
　　[D]involve employing surgical instruments
　　52．The word“rejuvenated”(Para．5)most probably means＿＿＿．
　　[A]modified 
　　[B]re—collected
　　[C]classified 
　　[D]reactivated
　　53．The research at the University of Wisconsin is mentioned to show＿＿＿．
　　[A ]the isolation of stem cells
　　[B]the effects of gene therapies
　　[C]the advantages of human cloning
　　[D]the limitations of tissue replacements
　　54．Which of the following is true according to the text?
　　[A]The principle of gene therapy is applicable to that of cloning．
　　[ B]The isolation of stem cells is too difficult to be feasible．
　　[C]It is reasonable for all body instructions to be activated．
　　[D]Cloned animals will eventually take control of the world．
　　55．Towards the genetic research．the author’s attitude can best be said to be that of＿＿＿．
　　[A]frustration 
　　[B]indifference
　　[C]amazement 
　　[D]opposition