Note B in the key of D major is the

Note B in the key of D major is the

  1. subdominant
  2. submediant ✓
  3. mediant
  4. dominant

Explanation

The D major scale has these notes: D, E, F#, G, A, B, C#. The submediant is the sixth note in any scale.

When we count from D (first note), B is the sixth note. This makes B the submediant of D major.

Remember: sub means six in music terms. The submediant is always the sixth scale degree.