(i) `because` There are 12 months in a year.
Therefore, the set of months of a year is finite
(ii) `because` The number of elements in the set `{1,2,3,…}` are indefinite
(iii) `because` The number of elements in the set `{1,2,3,…..,99,100}` are definite
(iv) In the set of positive integers greater than 100, the number of elements is indefinite
Therefore, set of positive integers greater than 100 is infinite
(v) `because` The number of prime integers less than 99 are finite
Therefore, set of prime numbers less than 99 is finite.