Final answer:
In a low-pressure system, the correct process is the air rising and cooling, which leads to cloud formation and potential precipitation. So the correct option is A.
Step-by-step explanation:
In a low-pressure system, the correct process that describes what happens to the air is A. Rising and cooling. When the earth's surface atmospheric pressure is lower than its surrounding environment, it causes the air to rise due to it being less dense. As the air rises, it carries moisture with it. The rising air currents cause water vapor to cool and condense, forming cloud formations, which is a key part of the water cycle involving condensation and precipitation.