Explanation:

Fourth option is correct i.e. Dehalogenation.

Dehalogenation is the process of removing the chlorine molecules from a contaminant in the soil. Contaminated soil is screened, processed with a crusher, and mixed with chemicals (i.e., reagents).). The mixture is heated in a reactor. The dehalogenation (i.e., dechlorination) process is achieved either: by replacing the chlorine molecules or by partially decomposing and partially volatizing contaminants.

Pyridine is used to dissolve other substances. It is also used to make many different products such as medicines, vitamins, food flavorings, paints, dyes, rubber products, adhesives, insecticides, and herbicides.