Final answer:
Frontal systems, specifically low-pressure systems, can cause clouds by adding moisture to the air through the movement of moisture and air within various weather fronts.
Step-by-step explanation:
Frontal systems, specifically low-pressure systems, can cause clouds by adding moisture to the air. When the air pressure is lower than the surrounding environment, moist air rises and condenses, producing clouds. This occurs due to the movement of moisture and air within various weather fronts. For example, in the case of cumulus clouds, water vapor rises because of convection, and the rise of clouds is driven by a positive feedback mechanism.