题目

第二节 完形填空（共15小题；每小题1分，满分15分）     阅读下面短文，掌握其大意，然后从36-50各题所给的四个选项（A、B、C和D）中，选出最佳选项。 Many years ago, I met with much difficulty with my life and work. I felt so  36 that I wanted to give up.  37  , a speech changed me. At the beginning of the speech, the well-known professor held up a $20 bill. In the room of 200 people, he asked, Who would   38  this $20 bill?Hands started going up. He said, “I am going to give this $20 to one of you, but first, let me do this.” He“m＞n＞0”是“方程mx2+ny2=1表示焦点在x轴上的椭圆”的（　　）A．充分不必要条件B．必要不充分条件C．既不充分也不必要条件D．充要条件