A:why
B:why that
C:that which
D:That
Jim stood up p____ when the lady came into the room. He is such a gentleman.
抛物线y2=4x的焦点F是椭圆x2a2+y2b2=1a>b>0的一个焦点,且它们的交点M到F的距离为53,则椭圆的离心率为( )
选择下列注音完全正确的一项( )