$A = (-9, 0)$ and $B = (-1, 0)$ are two points. If $P=(x,y)$ is a point such that $3PB = PA$, then the locus of $P$ is :

Question

( A ) $x^2 +y^2=3$
( B ) $x^2 - y^2 =-9$
( C ) $x^2 +y^2=9$
( D ) $x^2 - y^2=9$