题干
Have you heard of it? Firefighters rushed into a burning house, three of them unfortunately _______ in and ________ their lives.
A：catching; lost
B：caught; lost
C：caught; losing
D：catching; losing
答案(点此获取答案解析）
C
，设月球表面的重力加速度大小为
，在月球绕地球运行的轨道处由地球引力产生的加速度大小为
，则