The correct option is B U= {1, 2, 3, 4, 5, 6, 7, 8, 9}
Universal set is the set containing all the elements.
It contains all the elements of set A, set B and the remaining elements in the Venn diagram.
Hence the universal set is U= {1, 2, 3, 4, 5, 6, 7, 8, 9}