Which command effectively reduces the distance between ranks in a formation?

The command that effectively reduces the distance between ranks in a formation is "CLOSE RANKS, MARCH." This command instructs the troops to move closer together, thereby tightening the formation by decreasing the space between the ranks. It emphasizes the need for a more compact arrangement, which is particularly important for maintaining visual order and maximizing space during a parade or drill.

In contrast, the other commands focus on different aspects of military formations. "DRESS RIGHT, DRESS" is a command used to align the ranks along a straight line but does not specifically address the distance between those ranks; rather, it ensures that personnel are properly aligned side by side. "FORM SQUAD" is used to organize troops into a squad formation, which does not alter the distance between existing ranks but instead establishes a new organizational structure. "RANKS, FALL IN" is a command for assembling troops into ranks but does not indicate any specific adjustments to the spacing between those ranks.

Thus, "CLOSE RANKS, MARCH" specifically targets the reduction of distance between the ranks, making it the correct choice in this context.