题目

 The new teaching building ________ before the new term begins.        A. must be finished                            B. must finish                     C. must finished                                D. must being finished        答案：A已知双曲线x2a2-y2b2=1(a＞0，b＞0)的实轴长、虚轴长、焦距长成等差数列，则双曲线的离心率e为（　　） A、2B、3C、43D、53