题目内容
.
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
A
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题目内容
.
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
A