Passage:

Prevention is better than cure. It is recognised that the only way to get rid of malaria completely is to get rid of the mosquitoes which cause it. Malaria is always associated with damp and marshy land. This is not because the land is damp, but because the static water is the breeding place of the mosquitoes which begin their life as a larva in the water. Malaria does not frequently occur in dry desert countries because mosquitoes can not breed there. The only way to destroy mosquitoes is to prevent their breeding in static water. This can be done by draining all ponds and pools. And by keeping them covered in the breeding season with a film of kerosene oil which by depriving the larva of air, kills them.

Answer:

Mosquitoes, which cause Malaria, breed in stagnant water. They can not breed in dry lands. If we use kerosene, the stagnant water is covered with a layer of kerosene, the larva will die. By doing so, we could prevent the spreading of malaria.