The amount of coagulant needed for coagulation of water increases with (i) Increase in turbidity of water (ii) Decrease in turbidity of water (iii) Increase in temperature of water (iv) Decrease in temperature of water The correct answer is A. (i) and (ii) B. (i) and (iv) C. (ii) and (iii) D. (ii) and (iv)

The correct answer is (i) and (ii).

Coagulation is a process that is used to remove suspended particles from water. The amount of coagulant needed for coagulation increases with the increase in turbidity of water. This is because the higher the turbidity, the more suspended particles there are in the water, and the more coagulant is needed to destabilize and remove them.

The amount of coagulant needed for coagulation also increases with the decrease in temperature of water. This is because the lower the temperature, the less effective the coagulant is at destabilization and removal of suspended particles.

Options (iii) and (iv) are incorrect because the amount of coagulant needed for coagulation does not change with the increase or decrease in temperature of water.