阅读下面短文。从短文后所给的A、B、C三个选项中选出最佳选项。

    Light travels at a very fast speed. It is about a million times 1 than the speed of sound. You can get some idea of this 2 by watching the start of a race (赛跑). If you stand some distance away from the starter, you can see smoke from his gun before the sound gets to your 3

    This great speed of light4some strange facts. Sunlight 5about 8 minutes to get to us. If you look at the light of the moon tonight, 6 that the light rays (光线) left the moon 1.3 seconds before they got to you. The nearest star is so 7 away that the light which you can see from it tonight started to 8 towards you several years ago. In some cases, the light from one of tonight's stars had started on its journey to you before you were born.

    So, to be exact, we can't say, "The stars are shinning 9." We have to say instead, "The stars 10 pretty. They were shining several years ago, but their light has only just got to the Earth."

某班模拟了一次“红色旅游”的推介活动。下列主题适用于介绍井冈山的是（   ）

如图，轻弹簧上端与一质量为m的木块1相连，下端与另一质量为M的木块2相连，整个系统置于水平放置的光滑木板上，并处于静止状态．现将木板沿水平方向突然抽出，设抽出后的瞬间，木块1，2的加速度大小分别为a₁， a₂．重力加速度大小为g，则有（   ）