The correct options are
A p=q
B p2=q2
C q=−p
Equation of the given circle can be written as (x−p)2+(y−q)2=p2
so, that the centre of the circle is (p,q) and its radius is p.
This shows that x=0 is a tangent to the circle from the origin.
Since tangents from the origin are perpendicular, the equation of the other tangent must be y=0,
which is possible if q=±p or p2=q2