Question

The question that puzzles them is ___they can finish the work on time.

A．what it is that

B．what is it that

C．how is it that

D．how it is that

Answer 1

D

解析试题分析：句意：困扰他们的问题是他们究竟怎样才能按时完成工作。此处is之后是表语从句，表语从句由强调句型构成，相当于：it is how that they can finish the work on time.这里how是连词置于句首。故选D。
考点：考查强调句型及宾语从句的用法。