What is the likely consequence of a stuck mode door in an A/C system?

A stuck mode door in an A/C system primarily affects airflow direction and distribution within the vehicle's cabin. When the mode door is stuck, it may prevent air from being directed to the desired vents, leading to a situation where air does not flow efficiently or effectively. This results in reduced airflow, which can diminish the overall comfort level for occupants since they may not receive adequate heating or cooling in the cabin.

Inadequate airflow can also lead to other potential problems, such as poor defrosting capabilities in winter conditions. Therefore, option B is the correct choice as it directly addresses the primary impact of a malfunctioning mode door in an A/C system.