we need to have some practice( ) our theory.A .on which to base B .to base C.to baseD.on that to base 为什么选A！
问题描述：
we need to have some practice( ) our theory.A .on which to base B .to base C.to base
D.on that to base 为什么选A！
答
选A
定语从句中，当介词放在That之前时，That就要变成相应的Which或Who等等。
答
A
base on 固定搭配,在这里是介词前置了.