A、(<img width="13" height="36" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-23/ea25bc08-c495-4719-a80b-989521dec893.png" />+<img width="24" height="39" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-23/150f1b63-94cf-48a2-8aea-77e06d113a85.png" />)a
B、<img width="21" height="20" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-23/4e48caf2-cece-4c7f-b7d4-fb3b4b7cf17e.png" />a
C、(1+<img width="21" height="20" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-23/4ed963bd-1273-4b6b-8980-ff7f50916e2a.png" />)a
D、(1+<img width="21" height="20" src="http://admintk.100xuexi.com/UpLoadImage/2016-08-23/4acd80a7-9570-4b3d-a9db-beeb18507174.png" />)a