Answer:
A. 20 N.
Explanation:
The net force acting on an object is the sum of all the individual forces acting on it. In this case, the block is being pulled to the left with a force of 15 N and to the right with a force of 5 N at the same time.
The net force acting on the block is the sum of these two forces, which is 15 N + 5 N = 20 N.
Therefore, the correct answer is (A) 20 N.