【单选题】

Passage 3Human cloning technology could be used to reverse heart attacks. Scientists believe that they may be able to treat heart attack victims by cloning their healthy heart cells and injecting them into the areas of the heart that have been damaged, and other problems may be solved if human cloning and its technology are not forbidden.With cloning, infertile couples could have children.Current treatments for infertility, in terms of percentages, are not very successfully.Couples go through physically and emotionally painful procedures for a small chance of having children. Many couples run out of time and money without successfully having children. Human cloning could make it possible for many more infertile couples to have children than ever before.We should be able to clone the bone marrow for children and adults suffering from leukemi

A、This is expected to be one of the first benefits to come from cloning technology.We may learn how to switch cells on and off through cloning and thus be able to cure cancer. Cloning technology can be used to test for and perhaps cure gene-related diseases.The above is just a few examples of what human cloning technology can do for mankinD、This new technology promises unprecedented advancement in medicine if people will release their fears and let the benefits begin. According to the writer, the main problem with the development of human cloning technology is that___________.
A、it may be out of human control
B．it has brought about few benefits so far
C．people still know little about it
D．people are afraid of such technology