Which of the following collections are sets?

(i) The collection of all natural numbers less than 50 is a set because it is well defined.

(ii) The collection of good hockey players is not a set because the goodness of a hockey player is not defined here. So, it is not a set.

(iii) The collection of all girls in a class is a set, as it is well defined that all girls of the class are being talked about.

(iv) The collection of the most talented writers of India is a set because it is well defined.

(v) The collection of difficult topics in mathematics is not a set because a topic can be easy for one student while difficult for the other student.

(vi) The collection of all months of a year beginning with the letter J is a set given by {January, June, July}

(vii) A collection of novels written by Munshi Prem Chand is a set because one can determine whether the novel is written by Munshi Prem Chand or not.

(Viii) The collection of all question in this chapter is a set because one can easily check whether it is a question of the chapter or not.

(ix) A collection of most dangerous animals of the world is not a set because we cannot decide whether the animal is dangerous or not.

(x) The collection of prime integers is set given by {2, 3, 5........}