Answer:
D. 50 N
Step-by-step explanation:
The 2 forces of the cart will counteract each other because they are being pushed in opposite directions. The 150 N will counteract the 150 N on the other side. But since there's an extra 50 N on the left, it will push 50 N to the right. The 2 150 N will do nothing because they are pushing in opposite directions. For example, if two people are pushing something in the opposite direction with the exact same force, the pushed object won't move.