What is the union of the two sets r={10, 11, 13, 15, 17} and t={5, 7}?

null set

{5,7}

(5, 7, 10, 11, 13, 15, 17}

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.