问题
选择题
We can hear sound because our earth is surrounded by thick air _____ sound can travel.[ ]
A. in that
B. by which
C. with which
D. through which
答案
答案：D
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We can hear sound because our earth is surrounded by thick air _____ sound can travel.[ ]
A. in that
B. by which
C. with which
D. through which
答案：D