The correct option is C 40∘
PQR is a tangent. Thus, ∠OQR=90∘(Angle between tangent and radius)
Thus, ∠OQB=90−∠BQR
∠OQB=20∘
Let the line from O meet AB at M. Now In △MQA and △MQB
∠QMA=∠QMB (Each 90, as AB∥PR)
QM=QM (common)
MA=MB (Perpendicular from centre bisects the chord)
Thus, △QMA≅△QMB (SAS rule)
Hence, ∠MQA=∠MQB=20∘
Hence, ∠AQB=40∘