关于电场强度定义式<img src="/lqwvjeImg/05/05afd39aa3b0973b30e8da71c4aa7884.png"style="width:68px;height:25px;">,下列说法中哪个是正确的 ( )<br>· 场强<img src="/lqwvjeImg/15/1523b1e6a103b19d91e5639d72d31130.png"style="width:16px;height:20px;">的大小与试探电荷q0的大小成反比.<br>· 对场中某点,试探电荷受力<img src="/lqwvjeImg/ce/ce86cd981a2755ae7a71dbe081c8f095.png"style="width:17px;height:20px;">与q0的比值不因q0而变.<br>· 试探电荷受力<img src="/lqwvjeImg/ce/ce86cd981a2755ae7a71dbe081c8f095.png"style="width:17px;height:20px;">的方向就是场强<img src="/lqwvjeImg/15/1523b1e6a103b19d91e5639d72d31130.png"style="width:16px;height:20px;">的方向.<br>· 若场中某点不放试探电荷q0,则<img src="/lqwvjeImg/ce/ce86cd981a2755ae7a71dbe081c8f095.png"style="width:17px;height:20px;">=0,从而<img src="/lqwvjeImg/15/1523b1e6a103b19d91e5639d72d31130.png"style="width:16px;height:20px;">=0.