问题
单项选择题
The scientists are（）a series of experiments to learn more about how the body adapts to weightlessness.
A.defining
B.having
C.carrying
D.doing
答案
参考答案：D
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The scientists are（）a series of experiments to learn more about how the body adapts to weightlessness.
A.defining
B.having
C.carrying
D.doing
参考答案：D