问题详情

The possibility that a virus causes human cancer is indicated by ______.
A．the fact that viruses have been known to mutate
B．the fact that a cancer-immune individual may lose his immunity
C．the fact that production of human cancer cells might be due to a genetic factor
D．the fact that man is host to many viruses请帮忙给出正确答案和分析，谢谢！