Which feature of the M777A2 contributes to its mobility?

The lightweight design of the M777A2 is a crucial feature that significantly enhances its mobility. Weighing substantially less than many other towed artillery systems, the M777A2 can be easily moved by helicopters or tactical vehicles, enabling rapid repositioning in combat situations. This lightweight characteristic allows for greater flexibility on the battlefield, as troops can deploy the howitzer in various terrains and rapidly relocate it as tactical situations evolve.

In contrast, the other options touch on aspects that do not primarily support mobility. Heavy weight, while providing stability, can hinder movement and flexibility. Large tracks might be effective for mobility in certain vehicles, but the M777A2 is designed as a towed artillery piece rather than a self-propelled one, which makes this irrelevant. Finally, reliance on traditional towing vehicles does not enhance the inherent mobility of the howitzer itself; instead, it reflects the logistics of moving it, which is not as advantageous as the inherent lightweight design.