The number line sketched above shows the positions of both points A and B.
They both are the same distance from the point zero. However, while the measure of the distance is always a positive value, the value on the number line to the left is negative, while that on the right is positive. Therefore, adding both values (same value/distance) on both the left and rigt side will result in 0.
Whatever is the value of B on the number line, e.g, 3 units, then A will be the negative and adding;
The correct answer is option B