This puzzle asks you to find the single category linking five clues: Ghosts in Pac-Man, Grand Slams in tennis, Bases in DNA, Nations in the United Kingdom, and Train spaces in Monopoly (1/side). The answer is Things that come in groups of four. Each clue is a concrete example of a broader collection. The answer is the set label that every row belongs to without stretching the meaning. With only "Ghosts in Pac-Man", many categories could fit. Hold your first guess and watch what clue 2 eliminates. "Ghosts in Pac-Man" and "Grand Slams in tennis" must share one repeatable link — not a coincidence between two words. By clue 3 ("Bases in DNA"), "Things that come in groups of four" should explain all three without bending meanings. "Nations in the United Kingdom" strengthens "Things that come in groups of four" rather than opening a new theory. The final clue ("Train spaces in Monopoly (1/side)") confirms "Things that come in groups of four" — if it still fits naturally, the category is locked. Use the Solution tab above for an interactive clue-by-clue walkthrough, or the Solved board tab for the complete answer at a glance.