Question

It was said            was how the Chinese first raised silk worms.

A．that what

B．that which

C．that who

D．that that

Answer 1

D

本句中的it为形式主语，真正的主语是后面的由that 引导的主语从句that that was how the Chinese first raised silk worms，在这个主语从句中，第一个that 只起引导词的作用，第二个that 是指示代词，作从句的主语。