Is a mouse that can speak acceptable? How about a dog with human hands or feet? Scientists, the people with the know-how to make such things happen, are now thinking about whether such experiments are morally right or not.
On Nov. 10, Britain’s Academy of Medical Sciences launched a study on the use of animals with human materials in scientific research. The work is expected to take at least a year, but its leaders hope it will lead to guidelines for scientists in Britain and around the world on how far they can go mixing human genes into animals in search of ways to fight human diseases.
“Do these constructs (构想) challenge our idea of what it is to be human?” asked Martin Bobrow, a professor of medical genetics at Cambridge University and chair of a 14-member group looking into the issue. “It is important that we consider these questions now so that appropriate boundaries are recognized.”     
Using human material in animals is not new. Scientists have already created monkeys that have a human form of the Huntingdon’s gene so they can study how the disease develops; and mice with livers (肝) made from human cells are being used to study the effects of new drugs.
However, scientists say the technology to put ever greater amounts of human genetic material into animals is spreading quickly around the world --- raising the possibility that some scientists in some places may want to go further than is morally acceptable.
Last year in Britain there was a lively debate over new laws allowing the creation of human-animal embryos (胚胎) for experiments. On one side of the debate were religious groups, who claimed that such science interferes with nature. Opposing them were scientists who pointed out that such experiments were vital to research cures for diseases.
The experts will publish reports after the end of the study, in which they will give definitions for animal embryos with human genes or cells, look at safety and animal welfare issues, and consider the right legal framework to work within. 
72. What does the underlined word “they” in Paragraph 2 refer to?
A. Scientists in Britain and around the world.                
B. Leaders of the research.
C. Guidelines for scientists.                         
D. Scientific experiments.
73. Scientists do research of mixing human genes into animals in order to ____.
A. test new drugs on animals
B. to find ways to fight human diseases
C. prove the research is morally acceptable
D. create monkeys and mice with livers made from human cells
74. We can infer from the passage that ____.
A. the experts will release reports after the study
B. scientists have never doubted the use of animals with human materials
C. the creation of human-animal embryos for experiments is legal in Britain
D. religious groups hold that cures for diseases have to be done through experiments
75. What would be the best title of the passage?
A. Morally right or not?                   B. A debate about new laws
C. Cures for diseases                      D. Animal embryos with human genes