The correct option is A iii > ii > i
Here, we have to arrange given mixtures in the decreasing order of their particle size.
Sugar in water is an example of a solution and we know that the size of particles in a solution is less than 1nm.
Milk is an example of a colloid and particles of these mixtures have size ranging from 1-1000 nm.
Chalk in water is an example of a suspension and these mixtures have particles of size more than 1000 nm.
The correct order of size of particles is chalk in water > milk > sugar in water.