Which chemical substance is known for its ability to selectively kill living organisms?

The choice of a biocide is correct because biocides are chemical substances specifically designed to kill or control harmful organisms, including bacteria, viruses, and fungi. They have a broad application across various fields, including agriculture, medicine, and sanitation. The key characteristic of biocides is their ability to act selectively on living organisms, effectively managing populations of pathogens or pests that could be harmful to humans, animals, or crops.

In the context of mold remediation and prevention, biocides play a crucial role in ensuring that mold spores are effectively reduced or eliminated, thus preventing potential health risks and property damage.

While fungicides, antimicrobials, and pesticides also aim to eliminate specific types of organisms—fungicides primarily target fungi, antimicrobials target a broader range of microbial life, and pesticides focus on pests—they represent more specialized categories within the broader classification of biocides. Therefore, while all of these substances can kill living organisms, biocide encompasses a wider scope, making it the most accurate answer in this scenario.