自花授粉作物纯系发生遗传变异是由于（）。
A.自交分离
B.基因杂合性
C.基因型纯合化
D.天然杂交和基因突变
参考答案：D
一_______do you like monkeys and penguins?
一Because monkeys are very smart and penguins are very cute.[ ]
A. How
B. What
C. Why
D. How much
阳浮而阴弱
