Question

if the back - up heat system is a gas furnace
o electric back - up heat is required in the event of a no - gas situation
o an emergency heat switch is not required
o the indoor coil requires a vent
o the indoor coil must be downstream of (after) the furnace heat exchanger
o the furnace is typically located in the outdoor unit

Explanation:

In case of gas unavailability for a gas furnace backup heat system, electric backup heat is a common requirement to ensure heating continues. Other options are incorrect as an emergency heat switch may be needed, indoor coil venting and positioning are not directly related to this situation, and gas furnaces are typically indoor units.

Answer:

A. electric back - up heat is required in the event of a no - gas situation