It can be concluded from the passage that the immune systems of animals______.A.can be alt
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It can be concluded from the passage that the immune systems of animals______.
A.can be altered by electric shocks
B.can be weakened by conditioning
C.can be suppressed by drug injections
D.can be affected by frequent does of saccharin
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正确答案:B
解析:由本文可知,导致老鼠免疫力降低的手段是通过实验,使其形成对某事物的条件反射。选项B中的conditioning正是“条件反射”之意。A、C、D三项都过于具体了。故选B项。
