什么是盈余公积？公司法规定公司制企业法定盈余公积如何提取、提取比例是多少？法定盈余公积累计额达到多少时可不再提取？

The teacher set such difficult problems ______ nobody could work out _____ none of us passed the test.

A．as; that

B．that; as

C．/; that

D．as; as