Final answer:
Appliances containing CFC refrigerants can be evacuated to atmospheric pressure when there are leaks in the appliance that make evacuation to the prescribed level unattainable.
Step-by-step explanation:
Appliances containing CFC refrigerants can be evacuated to atmospheric pressure when there are leaks in the appliance that make evacuation to the prescribed level unattainable (option C). When there are leaks in the appliance, it becomes difficult to reach the desired pressure level during the evacuation process. Therefore, option C is the correct answer.