问题
选择题
Not until the early years of the 19th century ________ what heat was.
A．man did know
B．did man knew
C．didn't man know
D．did man know
答案
Ｄ
考察倒装句。Not until的句式放在句首时，后面的主句使用部分倒装的形式。故D正确。
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