The correct option is B PQ
The line segment joining two points on the circle and passing through the centre is the diameter. In this case, the line segments OA, OP and OQ join the centre of the circle (O) to a point on the boundary (A, P or Q). Thus, OA, OP or OQ are the radii. Line segment PQ is joining points P and Q, also passing through O. So, PQ is the diameter.