Massing the effects of fire aims to focus fires at which of the following?

Massing the effects of fire is a military tactic that concentrates firepower to create a significant impact on specific objectives. The focus is on critical points because these are vital locations or assets that have a substantial effect on the enemy's ability to function or maintain operational effectiveness. By targeting critical points, forces can demoralize the enemy, disrupt their plans, and create opportunities for friendly forces to maneuver or engage effectively.

In contrast, targeting random targets does not yield the same strategic advantage, as it lacks focus and can lead to inefficient use of resources. While enemy reinforcements and support vehicles are indeed important targets, they may not have the immediate critical impact that targeting critical points achieves, making option B the most effective choice for maximizing the effects of fire.