D 3/B
The D 3 chord consists of the D (Perfect unison) and F# (Major third) notes, with B as the bass note.

How to play the D 3/B chord
- Play B as the lowest bass note in the left hand
- Find D (Root) on the piano keyboard
- Add F# (Major third) — 4 semitones above D
- Press all 3 notes simultaneously to sound the D 3/B chord