I am not sure _________ from his home to school.

A．how far is it

B．how long it take him

C．how he gets

D．how often he goes to

选择的创造性作用表现为（）

A.加速有利变异的巩固和纯合速度

B.促进基因变异

C.减缓有利变异的巩固和纯合速度

D.将数量性状变为质量变异