The correct option is
B 90oPR=QR ....Tangents from an external point to the circle are equal.∴△RPQ is an isosceles triangle.
∴∠RPQ=∠PQR=45o ...base angles of isosceles triangle.
∠PRQ+∠RQP+∠QPR=180o ...angle sum property of triangle.
∠PRQ=180−45o−45o=90o.So, option B is correct.