题目

阅读表达：根据短文内容回答问题Bill’s father likes eating fish very much. He often buys fish in the shop and cooks it to eat. One day Bill sees the fish and thinks,” Good! Now, I can ask my friends to have lunch and we can eat the fish. They like fish very much. When father comes home from work in the evening, the fish is not there and Bill says, Oh, your cat eats it. And then he gives his father some rice for his supper. Father is angry. He takes the cat and Bill to a shop near his house and weighs(称) the cat.Then he turns to Bill and says, My fish weighs one kilo(公斤).（2005•杭州）若t是一元二次方程ax2+bx+c=0（a≠0）的根，则判别式△=b2-4ac和完全平方式M=（2at+b）2的关系是（ ）A．△=MB．△＞MC．△＜MD．大小关系不能确定