In a single throw of a die, consider the events A = {1, 2, 3} and B = {2, 4, 6}. The event (B − A)′ is equal to

(a) {4}

(b) {2, 4, 5, 6}

(c) {1, 3}

(d) {4, 6}

(e) {1, 2, 3, 5}.