Question

what is one of the problems with indoor air pollutants? they can build up to high concentrations they exist in small quantities they can easily blow away they cant build up

Explanation:

Indoor spaces often have limited ventilation compared to outdoor areas. This lack of proper air exchange means that pollutants (such as from cleaning products, furniture off - gassing, etc.) cannot disperse easily. As a result, they accumulate over time, reaching high concentrations which can be harmful to human health. Options like "they exist in small quantities" is incorrect as the problem is their accumulation. "They can easily blow away" is wrong because indoor air movement is restricted. "They can't build up" is the opposite of what actually happens in indoor environments.

Answer:

they can build up to high concentrations