3颗气象卫星与地心距离相等，并可同时覆盖全球地表，现假设地球半径为R，这3颗卫星距地球最短距离为（　　）。

A、R

B、2R

C、<img width="22" height="34" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-19/ada81a6d-3125-45be-ad58-f58eecd58bc7.png" />

D、<img width="23" height="30" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-19/a3e89aab-b21f-4c01-b48c-9e6363ae9166.png" />

C、<img width="22" height="34" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-19/ada81a6d-3125-45be-ad58-f58eecd58bc7.png">

D、<img width="23" height="30" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-19/a3e89aab-b21f-4c01-b48c-9e6363ae9166.png">

C、<img width="22" height="34" src="https://static.tiw.cn//s/tiw/p3/UpLoadImage/2016-08-19/ada81a6d-3125-45be-ad58-f58eecd58bc7.png">

D、<img width="23" height="30" src="https://static.tiw.cn//s/tiw/p3/UpLoadImage/2016-08-19/a3e89aab-b21f-4c01-b48c-9e6363ae9166.png">