题目

第三部分：阅读理解（第一节15小题，第二节５小题；每小题２分，满分4０分） 第一节：阅读下面的短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项，并在答题卡上将该项涂黑。                                Parents often believe that they have a good relationship with their teenagers. But last summer, Joanna and Henry noticed a change in their older son: suddenly he seemed to be talking far more to his friends than to his parents. “The door to his room is always shut.” Joanna noted. Ti一个空气平行板电容器，极板间距离为d，正对面积为s，充以电荷量Q后，极板间电压为U，为使电容器的电容加倍，可采用的办法是（ ）A．将电压变为一半B．将所带电荷量变为2QC．将极板正对面积变为2SD．将两极板间充满相对介电常数为2的电介质