题目

      32. With no one to ______ in such a frightening situation, she felt very helpless. A. turn on       B. turn off        C. turn around    D. turn to 答案：D1．磁感线可以形象地描述磁场的强弱和方向：磁感线上任一点的切线方向就是该点的磁场方向，磁感线越密处磁场越强．