Solution:
There is no odd natural number divisible by 2, so there will be no element in this set, hence it is a null set.
(b) There is only one even prime number which is 2i.e., there is a element, so it is not a null set
(c) There is no natural number which is less than 5 and greater than 7 i.e., there is no element, so it is a null set.
(d) Since, parallel lines never intersect each other, so they have no common point i.e., no element, so it is a null set.