In a group of 4 — J, K, L, M — at least one must be selected but not all four. J and K cannot both be selected. If L is selected, M must be selected. Which selection is valid?
✓ Correct Answer: Option C
{J,K} violates "J and K cannot both be selected." {L} violates "if L then M." {J,K,L,M} violates "not all four." {J,L,M} satisfies all constraints.