题目

—Look! Do you know ________man under the tree?—Sorry. It's too far to see ________clearly. A . this; him B . that; this C . this; her D . that; him 答案：D关于磁感线和电场线，下列说法中正确的是（ ）A．磁感线是闭合曲线，而静电场线不是闭合曲线B．磁感线和电场线都是一些互相平行的曲线C．磁感线起始于N极，终止于S极；电场线起始于正电荷，终止于负电荷D．磁感线和电场线都只能分别表示磁场和电场的方向