题目

From the time I lined up my dolls on the sofa in playschool, I wanted to be teacher. “Open your books,” I would   41   my teddy bear and dolls. Then I would   42   teach them whatever new things I had just   43   at school.       For me, dream was one thing, and   44   was quite another. My family was too poor to   45  my tuition. Finally, with others’ help, I attended a state university. However, I   46   needed more money to pay for my other expenses, so I found a part-time job,   47   test tubes in the science department. By then I believed a、b、c、d是匀强电场中的四个点，它们正好是一个矩形的四个顶点．电场线与矩形所在平面平行．已知a点的电势为20V，b点的电势为24V，d点的电势为4V，如图，由此可知c点的电势为（ ）A．4VB．8VC．12VD．24V