题目

 What a pity! Considering his ability and experience, he ____ better.    A. need have made             B. must have made   C. can have made              D. might have made   答案：D如图所示，a、b、c是一条电场线上的三点，电场线的方向由a到c，a、b间距离等于b、c间距离，用φa、φb、φc和Ea、Eb、Ec分别表示a、b、c三点的电势和场强，可以判定A．φa＞φb＞φc                                      B．Ea＞Eb＞EcC．φa φb=φb φa                              D．Ea = Eb = Ec