Which fish is useful for the biological control of mosquitoes?

Given below are two statements.
Statement $I$: Baculoviruses are pathogens that attack nematodes.
Statement $II$: Baculoviruses are used as biological control agents in ecologically sensitive areas as they are species-specific in their action.
In the light of the above statements, choose the correct answer from the options given below.

Fish like $Gambusia$ are introduced in ponds to control mosquitoes because they:

What is the definition/explanation of the term 'Nematophagous'?

The species of genetically engineered microorganism that is successfully used in the bioremediation of oil is .........

From which of the following is a natural insecticide obtained?