单项选择题

Not until the early years of the 19th century（）what heat is.

A．man knew
B．did man know
C．man did know
D．didn't man knew

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单项选择题

After searching for half an hour, she realized that her glasses（）on the table all the time.

A．had been lain
B．have been lying
C．were lain
D．had been lying

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