问题
选择题
In this technological era once took a century now only takes a month.
A．which
B．that
C．when
D．What
答案
答案：D
考查名词性从句。what once took a century now 做takes的主语，是主语从句。从句中缺少took的主语，故选what。
搜题请搜索小程序“爱下问搜题”