Final answer:
The best method for preventing poor air quality from becoming worse is (a) pre-contact control, where sources of pollution are eliminated or emissions reduced before affecting the environment.
Step-by-step explanation:
The question you're asking about is which control method is best for preventing poor air quality from becoming worse. The most effective method to improve indoor air quality is to control the sources of pollution, which can be considered a form of pre-contact control. This includes eliminating individual sources of indoor pollution or reducing their emissions before they can spread and affect air quality, which is usually more effective than addressing the pollutants after they have been released into the environment.
Point-of-contact control and post-contact control are steps taken during or after the pollution has occurred, respectively. Hazard control, on the other hand, can involve a variety of methods, including the removal of hazardous substances and implementing safety measures, which can indirectly affect air quality by managing potential sources of pollution.