The correct answer is C) A variable air volume system. A variable air volume (VAV) system is characterized by poor air distribution and ventilation, as well as low system heat loads. This is because a VAV system adjusts the volume of air delivered to each zone based on the heating or cooling demand, rather than maintaining a constant airflow. This can result in uneven air distribution and potential ventilation issues, especially in areas with low heat loads. The other options are incorrect because: A) A terminal reheat system is designed for better air distribution and ventilation, B) A single zone system maintains a constant airflow, and D) A dual duct system has two separate air streams for heating and cooling, which provides better control and distribution.