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举一反三
【单选题】Animal studies are under way, human trial protocols are taking shape and drug makers are on alert. All the international health community needs now is a human vaccine for the bird flu pandemic sweepin...
A.
it has strong side effect to the elderly.
B.
it may turn ineffective in a short period.
C.
it is useless in preventing the virus.
D.
it hasn’t been tested in humans.