D. He provided new equipment.
One way in which Caesar Augustus improved Rome's army was by providing new equipment. This ensured that the soldiers had access to better and more advanced weapons, armor, and military technology. By upgrading the equipment of the army, Caesar Augustus aimed to enhance their effectiveness, combat capabilities, and overall readiness. This improvement in equipment would have had a direct impact on the soldiers' morale and their ability to effectively engage in battles, thereby strengthening Rome's military power.