单项选择题

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

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单项选择题

From his experiment the king concluded that （）

A．the first word children learn in any language is "bread"
B．the Phrygian language was the oldest in the world.
C．the oldest word in any language is that of "bread"
D．the Phrygian language was the easiest in the world to learn.

单项选择题

22（）

A．Ours
B．Mine
C．Our
D．it