What is the greatest integer k which makes the statement "When we take any 6 subsets with 5 elements of the set {1,2,…,9}, there exist k of them having at least one common element." true?<spanclass=′latex−bold′>(A)</span>1<spanclass=′latex−bold′>(B)</span>2<spanclass=′latex−bold′>(C)</span>3<spanclass=′latex−bold′>(D)</span>4<spanclass=′latex−bold′>(E)</span>5