Given that ∠APB=θ, we have also been given that PA and PB are tangents.
Thus since angle between radius and tangent is 900(B→1),we get ∠AOB to be 180−θ as sum of all angles of a quadrilateral(PAOB) is 3600.
∴ D→4.
Now triangle OAB is isosceles.
∴ ∠OAB =∠OBA=θ/2.Thus C→2.
∠PAO=∠PAB+∠BAO
∴ 900=∠PAB+θ/2
Thus A→3.