问题描述:
[-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
A.man knew
B.did man knew
C.didn't man know
D.did man know
翻译并分析
问题解答:
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