(i) {1, 2, 3, 6}
(ii) {2, 3}
(iii) {M, A, T, H, E, I, C, S}
(iv) {1, 3, 5, 7, 9}
(a) {x : x is a prime number and a divisor of 6}
(b) {x : x is an odd natural number smaller than 10}
(c) {x : x is a natural number and divisor of 6}
(d) {x : x is a letter of the word MATHEMATICS}