Subani and Johny are the students of IX class. They are given two mixtures containing

a) copper sulphate in water

b) sand in water respectively and asked them to separate the components by filtration. Subani is unable to separate but Johny is able to separate components because of the

i) Filtration works based on pore size

ii) Filtration is employed when solid is insoluble in liquid

iii) Filtration works based on particle size

iv) Filtration is employed when solid is soluble in liquid

The correct reason is