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">
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