Question

_____ is estimated is that 300 million farmers will become urban dwellers in three decades.

A．It

B．As

C．That

D．What

Answer 1

D

考查主语从句。What is estimated是一个主语从句，what引导起这个主语从句，并在句中做主语。AB不能引导主语从句，C在主语从句中不充当任何成分。