题目内容：

[单选题]A．ccording to the passage which of the following is true?

[A] A fixed star refers a star that is always stationary on the sky.

[B] Scientists can tell the motion of the earth from the motions of other five planets.

[C] Ancient people had scanty knowledge about the movement of the stars.

[D] All the stars on the sky can be seen all the year around.