题目

 She wants to have good grades, _____ she doesn’t want to work hard. A. but                          B. so                          C. although  D. because 答案：A已知双曲线C：x2a2-y2b2=1（a＞0，b＞0）的右焦点为F，过F且斜率为3的直线交C于A、B两点，若AF=4FB，则双曲线C的离心率为______．