Which interval spans seven semitones?

• A. Minor seventh
• B. Major seventh
• C. Augmented fourth
• D. Perfect fifth

Answer: (D)

Spanning seven semitones corresponds to a perfect fifth. You can see this by counting semitones or by looking at letter names: from one note up to the note five steps away in the alphabet forms a fifth. For example, from C up to G is C-D-E-F-G, five letter names apart, and the semitone count from C to G is seven (C to C# is 1, to D is 2, to D# is 3, to E is 4, to F is 5, to F# is 6, and to G is 7). This seven-semitone distance is the defining amount for a perfect fifth in standard tuning. Other options involve six semitones (which would be an augmented fourth or a diminished fifth) or different counts entirely (a perfect fourth is five, a major seventh is eleven), so they don’t match the seven-semitone span.