问题
选择题
.They were __________ to produce carbon,nitrogen,water and other gases.
A．in time
B．at a time
C．at one time
D．on time
答案
答案：A
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.They were __________ to produce carbon,nitrogen,water and other gases.
A．in time
B．at a time
C．at one time
D．on time
答案：A