题目

You're in a department store and you see a couple of attractive young women looking at a sweater. You listen to their conversation:  “I can't believe it--a Lorenzo Bertolla! They are almost impossible to find. Isn't it beautiful? And it's a lot cheaper than the one Sara bought in Rome. ” They leave and you go over to see this incredible sweater. It's nice and the price is right. You've never heard of Lorenzo Bertolla, but those girls looked really stylish. They must know. So, you buy it. You never realize that those young women are employees of an advertising agency. They are actually paiF1、F2是双曲线－＝1的两个焦点，点P在双曲线上，G是PF1的中点，且PF1⊥PF2，则△GF1F2的面积是 [　　] A．B． C．11D．