If all the sets under examination are subsets of some set U then U is called a universal set. Given two sets A and B:

• The set of all elements of the sets A and B is called the union of A and B
• The set of all elements both A and B is called the intersection of A and B
• The set of all elements of A which are not in B is called the difference of A and B
• The difference of U and A is called the complement of A.

As also understood from the information given, the correct answer is D. The statements in the options I “The set of all elements of the sets A and B is called the union of A and B “, II  “The set of all elements both A and B is called the intersection of A and B.”, and III “The set of all elements of A which are not in B is called the difference of A and B. are correct. The statement in the option IV “The difference of U and A is called the complement of U.” is not correct because of the fact that the difference of U and A is not called the complement of A not U.