Final answer:
Temperature has the most significant impact on density altitude. At higher temperatures, air density decreases, resulting in a higher density altitude.
Step-by-step explanation:
Among the factors that affect density altitude, temperature has the greatest effect. As temperature increases, air molecules move more rapidly and spread apart, decreasing air density. This is evident as we observe altitude increases; for instance, at the summit of Mount Everest, the air density is significantly lower than at sea level. Humidity also affects air density, with higher humidity leading to lower air density, but this effect is not as pronounced as that of temperature. Pressure changes contribute to changes in density altitude, yet they are generally less variable than temperature on a day-to-day basis.