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【单选题】
在非洲的某些疟疾发病区,细胞贫血杂合子的相对生育率反而较正常人高。若以野生型纯合子的生育率为1,下列说法不正确的是?A.
细胞贫血杂合子的选择系数为正值,表示自然选择对该基因型起正向选择作用。
B.
细胞贫血杂合子的遗传负荷为负值,意味着细胞贫血杂合子生存能力强。
C.
细胞贫血杂合子生存能力强是由于杂合细胞性状对恶性疟原虫的抵抗力较强。
D.
在美洲的黑人人群中没有杂合子的相对生育率较正常人高的现象,说明基因或基因型的适合度随环境改变而改变。
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【单选题】Where is Miss Zhao? Look, ______. [ ]
A.
there is she
B.
there does she
C.
there she is
D.
there she does
【简答题】He called to say he would be late home-something had come ____ at the office.
【单选题】He called to say he would be late home—something had come _____ at the office.
A.
upon
B.
with
C.
to
D.
up
【单选题】He called to say he would be late home—something had come ( ) at the office.
A.
down
B.
out
C.
with
D.
up
【简答题】(2009年10月)剩余价值与利润从数量上看_______。
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