题目9单选题
如图所示,边长为<img src="https://tihai-oss-cloud.itihey.com/img/bb6b86a09c959d9e69447d8d7686689e.png">的正方形的四角,依次放置点电荷<img src="https://tihai-oss-cloud.itihey.com/img/8c8c627fad82af0f9c10f7807822a59c.png">和<img src="https://tihai-oss-cloud.itihey.com/img/e033e315f413d094dccd5d14aef30273.png">,它的正中央放着一个单位正电荷,则这个电荷受力的大小和方向分别为:<img src="https://tihai-oss-cloud.itihey.com/img/c6fe7febbad94d864697d84e4195be23.png">A. <img src="https://tihai-oss-cloud.itihey.com/img/0003652c71b282d2adaf3b5eeddc8c81.png">,受力平衡B. <img src="https://tihai-oss-cloud.itihey.com/img/a694270e5253453967eced552fcb503c.png">,由中央电荷指向点电荷<img src="https://tihai-oss-cloud.itihey.com/img/d4773a08d61b1dd5ee7baeb4176983fa.png">C. <img src="https://tihai-oss-cloud.itihey.com/img/a694270e5253453967eced552fcb503c.png">,由中央电荷指向点电荷<img src="https://tihai-oss-cloud.itihey.com/img/5e1882b168b08cef3267da18e64185bc.png">D. <img src="https://tihai-oss-cloud.itihey.com/img/2d32f482d8c4e831e1bde38eb55f4529.png">,由中央电荷指向点电荷<img src="https://tihai-oss-cloud.itihey.com/img/d4773a08d61b1dd5ee7baeb4176983fa.png">