Let be a set of ten distinct positive integers, each less than . Which of the following must be true?
A contains two elements whose sum is .
B contains three elements in arithmetic progression.
C contains two elements whose difference is .
DThe elements of have sum at least .
E has two disjoint non-empty subsets with the same sum.
F contains two elements, one of which divides the other.
G contains a multiple of .
HThe largest element of is at least .