Final answer:
In sub-polar low-pressure systems, air typically rises and converges, leading to the formation of clouds and potential precipitation.
Step-by-step explanation:
In sub-polar low-pressure systems, the typical atmospheric behavior is characterized by air rising and converging. This happens because the air in these regions is cooler and denser than the warmer air above it. As the cool air sinks, it creates a vacuum that draws in warmer, moist air from the surrounding environment. This process causes the warm air to rise, and as it ascends, it cools and condenses to form clouds. The correct answer to the question is A) Air is rising and converging.