From a point P outside of a circle with centre O, tangent segments PA and PB are drawn. If ∣OA∣21+∣PA∣21=161, then AB=?
<spanclass=′latex−bold′>(A)</span>4<spanclass=′latex−bold′>(B)</span>6<spanclass=′latex−bold′>(C)</span>8<spanclass=′latex−bold′>(D)</span>10