First-class players of football must have excellent ball control, but it is not just _____ they do with their feet _____ counts.
A:how; that
B:that; what
C:what; that
D:whether; what
我国实行计划生育,但近年来每年新增人口仍达600多万,主要原因是( )
养鱼缸里经常要放一些新鲜的水草,这样做的主要目的是( )