The pesticide DDT slowly changes to

p, p-dichlorodiphenyldichloroethene

The correct answer is option 1. p, p-dichlorodiphenyldichloroethene.

DDT is a stable compound, but it can slowly degrade under the influence of sunlight and heat. The degradation of DDT produces p, p-dichlorodiphenyldichloroethene, which is a less toxic compound.

The other answer choices are incorrect. (2) is the chemical formula for p, p'-dichlorodiphenyldichloroethane, which is a more toxic compound than DDT. (3) is the chemical formula for p, p'-dichlorodiphenylethene, which is a highly reactive compound that is not found in nature. (4) is the chemical formula for \(CCl_3-CHO\)and chlorobenzene, which are not produced from the degradation of DDT.