已知两点M(-2，0)，N(2，0)，点P满足=12，则点P的轨迹方程为(    )

A.+y²=l         B．x²+y²=16        C．y²-x²=8        D．x²+y²=8

A.y²=8x                                             B.y²=-8x

C.y²=4x                                             D.y²=-4x