[-B32] It was not until the early years of the 19th century that _______ what heat was.

题目

[-B32] It was not until the early years of the 19th century that _______ what heat was.
A.man knew
B.did man knew
C.didn't man know
D.did man know
翻译并分析

答案

人们直到十九世纪初期才知道暖气是什么.
因为前面有了一个that,后面要加完整句子,后面的选项只适用于没有that的情况下.
如果没有that,那么not until 后面要谓语前置,而直到才,not until .did .do 则应该选D