The correct option is B 5000gf cm
The turning effect of a force is known as the moment. It is the product of the force multiplied by the perpendicular distance from the line of action of the force to the pivot or point where the object will turn. That is, Moment = Force * distance.
If the moment of a force turns or rotates the body in clockwise direction, then it is called clockwise moment.
In this case, the weight of 250 gf at the distance of 20 cm from the center point O, rotates the ruler in the clockwise direction.
Therefore, the clockwise moment is given as Clockwise moment=Force×arm distance.
That is, Clockwise moment= 250gf×20cm= 5000gf−cm.
Hence, the anticlockwise moment in this case is 5000 gf-cm.