Official 51 Lec 4
Question 4 of 6
According to the professor, 400 years ago what was believed to be true about Earth's atmosphere?

A.

It prevented high-speed motion of objects on Earth.

B.

It would only move if Earth moved.

C.

It was not affected by the motion of the Sun.

D.

It was not held down by any force.

正确答案:D

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