/d/ → /b/
The plosive alveolar /d/ becomes a plosive bilabial /b/ when it’s followed by a bilabial sound, such as /p/, /b/ or /m/, because of assimilation. The change only affects the place of articulation, but the manner of articulation (plosive) and the voicing (voiced) remain the same.
/d/ (followed by /p/, /b/ or /m/) becomes /b/
And now some examples from real life: