Which of the following activities can diminish air quality?

All of the activities listed can significantly diminish air quality in a laboratory or work environment. When working with volatile chemicals on an open bench, these substances can easily evaporate and release harmful vapors into the air, posing inhalation risks to anyone in the vicinity.

Leaving liquid waste containers uncapped can further degrade air quality as volatile compounds from these containers escape into the atmosphere, potentially leading to toxic inhalation and exposure risks.

Discharging volatile chemicals into the drain contributes to air pollution and can also cause harmful reactions that may release gases into the air, thus compromising air quality.

Considering each action's potential impact on both air quality and overall safety, it is clear that all of these activities are detrimental, which is why the answer encompasses all the listed options.