题目

The pilot asked all the passengers on board to remain _________ as the plane was making a landing.        A. seat    B. seating       C. seated D. to be seating 答案：C5．已知双曲线$\frac{{x}^{2}}{{a}^{2}}$-$\frac{{y}^{2}}{{b}^{2}}$=1，（a，b＞0）的左右焦点为F1、F2，过F2的直线交双曲线的右支于M、N两点，若|PF1|=|F1F2|，且2|PF2|=$\sqrt{2}$|QF2|，则该双曲线的离心率为7-4$\sqrt{2}$．