Malaria is a disease that is spread by mosquitoes. Mosquitoes lay eggs in stagnant water. Which of the following methods would help to control the number of mosquitoes? (i) Taking medicines that prevent malaria.

(ii) Put a thin film of oil on the surface of the water in a big pool.

(iii) Keeping the surroundings dry.

(iv) spraying chemical that kills insects.

Only (i)

Only (ii) and (iii)

Only (i), (ii) and (iii)

Only (ii), (iii) and (iv)