Research advances over the past decade have told us that, with a little work, we humans can clone just about anything we want, from frogs to monkeys and probably even ourselves!
So, we can clone things, but why would we want to?
Of all the reasons, cloning for medical purposes has the most potential to benefit large numbers of people. How might cloning be used in medicine?
1. Cloning animal models of disease
Much of what researchers learn about human disease comes from studying animal models such as mice. Often, animal models are genetically engineered to carry disease-causing mutations(变异) in their genes. Creating these transgenic（转基因的） animals is a time-intensive process that requires trial-and-error and several generations of breeding（培育）. Cloning technologies might reduce the time needed to make a transgenic animal model, and the result would be a population of genetically identical animals for study.
2．Cloning stem cells(干细胞) for the treatment of diseases
Stem cells are the body's building blocks, responsible for developing and repairing the body throughout life. As a result, they might be used to repair damaged or diseased organs and tissues. Researchers are currently looking up cloning as a way to create certain human stem cells for the research of diseases.
3. Cloning farm animals for drug production
Farm animals such as cows, sheep and goats are currently being genetically engineered to produce drugs or proteins that are useful in medicine. Just like creating animal models of disease, cloning might be a faster way to produce large herds of genetically engineered animals.
From Purpose One, we can infer that      .

A．most transgenic animals are clone

B．most animals carry engineered genes

C．most transgenic animal models are not cloned

D．most animals carry disease-causing mutations in their genes

It can be learned from Purpose Two that cloning technologies can be mainly use do    .

A．create damaged or diseased organs and tissues

B．clone genetically defined human stem cells

C．develop and maintain the body

D．repair the body throughout life

According to Purpose Three, cloning technologies can be mainly used to      .

A．speed up the producing of genetically engineered animals

B．produce drugs or proteins that are useful in medicine

C．raise genetically engineered cows, sheep and goats

D．produce large herds of animals for human beings