The statements regarding to sets in the options;

I “The sets A = {4, 8, 11, 15} and B = {8, 15, 4 ,11} are the same.”

II “The empty set Ø is a subset of any set.”

III “The equality A = B is equivalent to two inclusions: A ? B and B ? A.”

IV “The set of elements that are in either A or B or both is called the union of the sets A and B and is denoted by A ? B.”

V “x ? A ? B if and only if x ? A and x ? B.”

VI “If A ? B = Ø then the sets A and B are called disjoint sets.” are correct, so the correct answer is D.

The statement in the option VII “Universal set is unique.” is not correct. Universal set is not unique. It varies depending on the problem.