问题
选择题
.
It was ______ the 19th century_____ heat was considered to be a form of energy.
A．not until; that
B．until; that
C．not until; when
D．until; when
答案
答案：A
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.
It was ______ the 19th century_____ heat was considered to be a form of energy.
A．not until; that
B．until; that
C．not until; when
D．until; when
答案：A