(i) It is a set. As we are saying all numbers less than 50 it is a definite quantity hence it is a set.
(ii) It is not a set. Because when we say good hockey players, it changes opinion wise and cannot be well defined or is not countable.
(iii) It is a set. As we are saying a collection of all the girls in your class it is a definite quantity hence it is a set.
(iv) It is not a set. Because when we say a collection of all talented writers of India, it changes opinion wise and cannot be well defined or is not countable.
(v) It is not a set. Because when we say a collection of all talented writers of India, it changes opinion wise and cannot be well defined or is not countable.
(vi) It is a set. As we are saying a collection of novels written by Munshi Prem Chand.it is a definite quantity hence it is a set.
(vii) It is a set. As we are saying a collection of all the questions in this chapter. It is a definite quantity hence it is a set.
(viii) It is a set. As we are saying a collection of all months of a year beginning with the letter J. It is a definite quantity hence it is a set.
(ix) It is not a set. Because when we say a collection of most dangerous animals of the world it changes opinion wise and we cannot define dangerousness of an animal.
(x) It is a set as we are saying a collection of prime integers. It is a definite quantity hence it is a set.