A:6
B:7
C:8
D:9
我国探月卫星成功进入了绕“日地拉格朗日点”的轨道,我国成为世界上第三个造访该点的国家,如图所示,该拉格朗日点位于太阳与地球连线的延长线上,一飞行器位于该点,在几乎不消耗燃料的情况下与地球同步绕太阳做圆周运动,则此飞行器的( )
若a,b∈R,且ab>0,则下列不等式中,恒成立的是 ( )
Mr. Zhang can't speak French. _______, he had never learned French before he came to Paris.
— What is this English?
— It's a quilt.