正在空中飞行的物体B重50N，在图中画出物体B所受力的示意图（不计空气阻力）

The advantage of geostationary satellites is（）.

A.the range of antenna can cover everywhere in the world

B.we can know the ship’s exact position

C.that the distress alert can be located as soon as possible

D.antenna of permanent earth stations may be directed towards fixed points in the sky