题目

I'm going to the supermarket to buy some _________ this afternoon. A . paper and pencil B . apples and banana C . milk and eggs D . bowl and tofu 答案：C设，是双曲线，的左、右两个焦点，若双曲线右支上存在一点，使（为坐标原点），且，则双曲线的离心率为 （ ）A． B． C． D．