An air conditioning unit turns off once it reaches its goal temperature. The house warms up and the air conditioning unit turns on again. When the air conditioning unit turns on, it is an example of:

A)input

B)process

C)output

D)feedback

D) feedback.

Explanation:

An air condtioning unit consists of the following elements according to available choices:

Inputs: Refrigerant, air from surroundings, electricity.

Process: Refrigeration cycle.

Output: Conditioned air at goal temperature.

Feedback: Activation and deactivation of the air conditioning unit depending on indoor temperature.

When the air conditioning turns on and off to keep goal temperature indoors, a control stage consisting in a controller and a action element is acting to reverse the behavior of the process with a view to keep goal temperature.

Hence, correct answer is D.