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【单选题】人们曾采用将轻症天花病人的“痘浆”接种到健康人身上来预防天花，这里所说的痘浆和这种方法分别属于（）。
A.
抗原、特异性免疫
B.
抗体、特异性免疫
C.
抗原、非特异性免疫
D.
抗体、非特异性免疫
【单选题】Many people feel that human beings are responsible for the disappearance of some other animal species. While we may have hastened the disappearance of some, abundant evidence suggests mankind has had ...
A.
Human beings have hastened the disappearance of some.
B.
There was mass extinction long before humanity's time on Earth.
C.
Human beings'activities have had great impact on the earth.
D.
Many species have extinct since the human race came into being.