Question

It hasn't been made clear ________ the new underground line is to be open to traffic.

A.whenB．that

C．whatD．where

 

Answer 1

A

【解析】A 考察名词性从句。这是when引导的主语从句，it是形式主语。句意：新的地铁线路何时开放还不清楚。故A正确。