问题详情

Cancer should be considered to be a biological problem rather than a medical one because ______.
A．viruses are known to cause cancer in animals
B．at present, human cancer is not believed to be contagious (传染的)
C．there are many known causes for the transformation of a normal cell to a cancer cell
D．results of experiments on plants and animals do not vary greatly from species tn species请帮忙给出正确答案和分析，谢谢！