Which of the following pairs of sets are disjoint

Which of the following pairs of sets are disjoint?
(i) {1, 2, 3, 4} and {x: x is a natural number and 4 ≤ x ≤ 6} 
(ii) {a, e, i, o, u} and {c, d, e, f}
(iii) {x: x is an even integer} and {x: x is an odd integer}
Answer
(i) let A = {1, 2, 3, 4} and B = {x: x is a natural number and 4 ≤ x ≤ 6} = {4, 5, 6}
Now, A ∩B = {1, 2, 3, 4} ∩ {4, 5, 6} = {4}
Intersection of both set is not a null or void set. Therefore, this pair of sets is not disjoint.
(ii) let A = {a, e, i, o, u} and B=(c, d, e, f} = {e}
Now, A ∩B = {a, e, i, o, u} ∩ (c, d, e, f} = {e}
Intersection of both set is not an empty or null set. Therefore, this pair of sets is not disjoint.
(iii) Let A = {x: x is an even integer} = {2, 4, 6, 8....} and B = {x: x is an odd integer} ={1, 3, 5, 7, ...}
A ∩B = {2, 4, 6, 8....} ∩ {1, 3, 5, 7...} = Φ
Intersection of both set is an empty or null set. Therefore, this pair of sets is disjoint.