Unless a seal is designed to impound water, the seal shall be provided with a means of:

The correct choice is centered on the importance of safety and monitoring conditions in sealed areas of a mine. When a seal is established to prevent the passage of air or gases, it is imperative to have a mechanism for assessing the air quality behind the seal. This is particularly crucial because hazardous gases can accumulate in sealed areas, posing serious risks to miners' health and safety if those areas become compromised.

By having a means of checking air quality, ventilation and emergency response teams can ensure that the atmosphere behind the seal remains safe, or take necessary actions if it does not. This capability allows for ongoing assessment and helps prevent dangerous situations before they develop, aligning with mining safety regulations and practices.

Other options, such as estimating air pressure or monitoring temperature, do not directly address the urgent need for air quality assessment in potentially hazardous environments like sealed areas. While these factors are relevant to overall mine safety, they do not replace the critical need for air quality monitoring specifically behind a seal designed to maintain safety from gas accumulation.