(a) 1∈ A but 1∉ B and 6 ∈ B but 6 ∉ A.
∴ A and B are not comparable.
(b) A = {x: x ∈ N and x ≤ 10} = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} B = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}
Clearly, A ⊂ B ⇒ A and B are comparable.
(c) {4, 5} ∈ A but {4, 5} ∉ B and 4 ∈ B but 4 ∉ A.
∴ A and B are not comparable.
