(i) The number of industries is increasing continuously. Water used by most of the industries is drawn from the ground so this contributes to water depletion.
(ii) Increasing population creates demand for construction of houses, shops, offices, roads and pavements. This decreases the open areas like fields, parks, and playgrounds. This, in turn, decreases the seepage of rainwater into the ground, which in turn leads to water depletion.
(iii) Heavy rainfall increases the level of water table. It doesn't deplete the water.
(iv) A majority of farmers in India depend upon rains for irrigating their crops. Farmers also use groundwater for irrigation. Extensive agricultural activities may cause water depletion.
So the correct answer is option (iii) Heavy rainfall.