What is the purpose of a plenum thermostat?

Question

A) To control the plenum heat strips that prevent the supply air temperature from dropping too low
B) To control the heating and cooling equipment to maintain the desired temperature in the supply plenum at all times
C) To cycle off the heating or cooling equipment if the air gets too hot or cold in the plenum when only one or two zones are calling
D) To control the zone dampers based on the plenum temperature

Answer 1

C