Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?

Emulsification occurs between two immiscible liquids. So (i) is not possible.

River water itself is a colloidal sol due to the presence of clay particles. But when river water meets with sea-water it doesn’t remain a colloidal solution, because sea-water contains electrolytes. So (ii) is not correct.

River water when comes in contact with the salty water of sea, the electrolytes present in sea-water brings coagulation of clay particles and thus delta is formed. Clay particles in river water are negatively charged and thus when combines with positively charged ions in sea-water coagulation take place. Therefore, option (iii) is correct.

Peptisation is a process of converting a precipitate into colloidal sol when shaken it with dispersion medium in the presence of small amount of electrolyte. So (iv) cannot be the correct option.