已知点A(-1,0),B(1,0),P是平面内一动点,直线PA,PB斜率之积为−
A.2x2+y2=1(x≠±1)
B.x2+2y2=1(x≠±1)
C.x2-2y2=1(x≠±1)
D.2x2-y2=1(x≠±1)