Explanation:
Let us understand the term DDT
DDT : Dichlorodiphenyltrichloroethane
It killed off bird populations: Though it does not kill birds directly by consuming, it has indirectly damaged the egg by making the egg's shell too thin which gets broken easily.
It controlled diseases like malaria: Since this option talks about positive attribute of DDT, this option stands invalid. This chemical compound controls mosquitoes attacking the crop.
It caused harm to human populations: DDT causes vomiting, tremors or shakiness, and seizures
It contained toxins: It contains moderate toxins.