Considering,
(i) Controlling flood
(ii) Generating hydropower
(iii) Preventing loss of water in percolation from fields
(iv) Sewage disposal. A reservoir is used for
Correct answer is

Explanation:

A reservoir is an artificial or natural lake used to store water for various purposes. Two of the most important functions of reservoirs are:

• Controlling floods — Reservoirs regulate river flow by storing excess water during heavy rainfall or snowmelt, releasing it gradually to prevent downstream flooding.

• Generating hydropower — Reservoirs provide a constant supply of water to hydropower plants. The stored water is released through turbines to generate electricity, making use of the potential energy of the stored water.

 Additional Informatio

• Multi-purpose reservoirs serve various functions such as irrigation, drinking water supply, recreation, and navigation, in addition to flood control and power generation.

• Flood storage capacity of a reservoir is the volume available to store floodwaters temporarily.

• Hydropower generation depends on both the head (height of water) and flow rate — both managed by the reservoir.

• On the other hand, preventing percolation from fields and sewage disposal are not primary functions of a reservoir.