同心球形电容器，两极的半径分别为R1和R2（R2＞R1），中间充满相对介电系数为εr的均匀介质，则两极间场强的分布曲线为（　　）。

A、<img width="160" height="153" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/cfc57ff9-6b84-4ddc-aec5-fe02efba2a43.png" />

B、<img width="160" height="154" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/fc933e49-8991-4901-9a13-46647bbcaee3.png" />

C、<img width="151" height="146" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/27b9c88b-152b-4a95-8e77-943ef290b386.png" />

D、<img width="158" height="140" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/afd2f55a-2998-49e4-b6a4-48afec1d198c.png" />