Residential HVAC Installation Practice Exam

Ordinary clean refrigerant oil can generally be used satisfactorily in a vacuum pump, as long as it is not contaminated by moisture or other impurities. Option A is incorrect because while it may not be recommended, it is still commonly used. Option B is incorrect because the suitability does not depend on specific temperatures. Option D is incorrect because it is not strictly prohibited, although certain types of oils may not be compatible with certain vacuum pump systems and precautions should be taken.