(i) Number of elements in given set = 1 Number of subsets of given set = $2^1$ = 2 ∴ Subsets of given set are ϕ, {a}. (ii) Number of elements in given set = 2 Number of subsets of given set = $2^2$ = 4 ∴ Subsets of given set are ϕ, {a}, {b}, {a, b}. (iii) Number of elements in given set = 3 Number of subsets of given set = $2^3$ = 8 ∴ Subsets of given set are ϕ, {1}, {2}, {3}, {1, 2}, {2, 3}, {1, 3}, {1, 2, 3}. (iv) Number of elements in given set = 0 Number of subsets of given set = $2^0$ = 1 ∴ Subset of given set is ϕ.