长度为L、横截面积为S，电阻率为β的的某种材料的电阻为（）。

A、<img src="https://img.ppkao.com/2017-05/xuyiying/2017050408341691398.jpg">

B、<img src="https://img.ppkao.com/2017-05/xuyiying/2017050408342615420.jpg">

C、<img src="https://img.ppkao.com/2017-05/xuyiying/2017050408343380337.jpg">

D、<img src="https://img.ppkao.com/2017-05/xuyiying/2017050408343863420.jpg">