.I find _____very difficult to understand people who speak fast.

问题描述:

.I find _____very difficult to understand people who speak fast.
A .that B.this C.it D.it's
为什么答案是C而不是D

C
sb.find/found it + a.+ to do sth.
某人发现做某事很...
这是个固定句型,此句型里的it不可用其他词代替