The correct option is C 4.4Nm(clockwise)
Moment is defined as rXF Here r is nothing but perpendicular distance from the force to that point O. Given the distances as 0.9 m, 0.8m, 0.6m for A,B,C respectively from point O. All has same magnitude of force that is 4 N. Hence
For A
moment=0.9×4=3.6N−m
For B
moment=0.8×4=3.2N−m
For C
moment=0.6×4=2.4N−m.
Here A and B as both are in the clockwise direction where C gets subtracted as it is in an anti-clockwise direction. Hence resultant torque is
3.6+3.2−2.4=4.4N−m.
Hence 4.4N−m is the resultant torque.