Final answer:
4) Farming is not one of the primary industries involved in toxic release when compared with mining, chemical production, and electric utilities, which are known to handle hazardous substances and heavy metals.
Step-by-step explanation:
The industry that is NOT one of the primary industries involved in toxic release among the options provided is farming. This is because industries like mining, chemical production, and electric utilities are known for their significant contributions to environmental pollution, including toxic releases. These industries often deal with hazardous substances and heavy metals that can contaminate air, water, and soil. Farming, while it can contribute to pollution through pesticides and fertilizers, is generally not considered a primary source of toxic releases in comparison to the heavy industrial activities of the other mentioned sectors.