___seems easy in theory may be difficult in practice.A、ThatB、WhichC、WhatD、It

___seems easy in theory may be difficult in practice.A、ThatB、WhichC、WhatD、It
___seems easy in theory may be difficult in practice.
A、That
B、Which
C、What
D、It

___seems easy in theory may be difficult in practice.A、ThatB、WhichC、WhatD、It
c

C
前面缺少主语，要用what
意思是在理论上很容易的事情，在实践中会变的很复杂。
what指什么事情

c

D
It 是Seems 的主语，是整句话的主代。

C

肯定了D

C
What seems easy in theory may be difficult in practice.
what引导的从句作主语。

用排除法,B、C明显不可以，而that 主要起一个承接作用，现在没有这种前后关系只有D是对的