[题目]一电场强度为E的均匀电场,E的方向与-|||-x轴正向平行,如图所示。则通过图中一半径为R-|||-的半球面的电场强度通量为 ()-|||-E-|||-x-|||-A. pi (R)^2E-|||-B. dfrac (1)(2)pi (R)^2E-|||-C. pi (R)^2E-|||-D.0