A．It is an active ingredient in a foam, cream or suppository.
B．It is an active ingredient applied before sex to prevent HIV transmission.
C．It is a protein that protects the body from infection by microorganisms.
D．It is a drug used to prevent HIV transmission.
参考答案C
解析:
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A．meat canning, a tradition in American church groups.
B．American church groups' canning food for those in need.
C．how to can food in American church groups.
D．the canned food delivery all over the world.
A．5 hours.
B．10 hours.
C．17 hours.
D．20 hours.
