Answer:
A and E
Step-by-step explanation:
An easy (calculation free) way to think about it is balance. The question states that the system is un-moving and therefore balanced in the picture. To keep it balanced, we want to add equal weights at equal distances on opposite sides of the pivot point. A and E are both 2 holes away from the pivot point.
The actual (physics) explanation for this is using torques. The system is balanced in the picture since the center of mass of the bar is at D and the weight is at B. They are equal distances and weights from the pivot point, and cause torques of equal magnitude in opposite directions from each other, so the net torque is 0. We want to apply the same logic when adding 2 more masses. Torque = r F sinα, where r is the distance from the pivot point and F is the weight (force of gravity). Since F is down in both cases, they will cause torques in the opposite directions. To get a net torque of 0 (balanced), we want the torques to have equal magnitude in opposite directions, so as long as r (the distance from the pivot point) is equal for each mass, the system will remain balanced.