Answer:
(2) acting as natural selecting agent
Step-by-step explanation:
Compounds like the pesticide DDT may bring about the evolution of new strains of organisms by acting as a natural selecting agent.
Evolution is generally defined as a gradual change to the characteristics of organisms over a period of time.
When DDT is used on a particular population of pest, those that are weak within the population die off, leaving only those that are strong within the population to survive and multiply. The DDT acts a selecting agent for the survival gene in the pest and the survived gene eventually evolve into a new, DDT-resistant strain pest in no time.
The correct option is option (2).