Mathematics > sets-relations-and-functions > Sets

Which of the following are examples of the null set
(i) Set of odd natural numbers divisible by 2
(ii) Set of even prime numbers
(iii) $\{x : x \text{ is a natural numbers, } x < 5 \text{ and } x > 7\}$
(iv) $\{y : y \text{ is a point common to any two parallel lines}\}$