Is there such a thing as being “over-protective”?

    I can honestly say that my answer____that question has changed dramatically（戏剧性地）since I became a parent.

    Before the birth of my daughter,I taught at a private school,often____(view) my students as over-protected, worrying____would happen to them when they went on to middle schools.

    Some did fine,and some did not.Some needed constant pats on the back,words of encouragement and extra support,which I____(happy) gave.Others____(satisfy) with themselves,needing little or no interaction（互动）with their teacher.____for the most part,graduates would go on for higher schooling.

    I'd always taken it for granted____their parents were over-protective,for they were the ones that still walked their____(five) graders into the classroom and met them at the school gate.

    Admittedly,I laughed at those parents,thinking their children would never learn to be____(dependent) if they didn't let go just a little.Then I had my own daughter. The moment I looked at her little face,I knew I'd do everything in my power____(protect) her and make sure she always felt safe!

一个点电荷，从静电场中的$a$点移到$b$点，其电势能的变化为零，则 (    )

费正清教授曾把一战期间中国民族工业的发展称为“没有前途的经济奇迹”。这主要是因为