/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/
It could be better. ǀ kʊb bi ˈbetə ǀ
You could publish it. ǀ kʊb ˈpʌblɪʃ ɪt ǀ
She could modify it. ǀ kʊb ˈmɒdɪfaɪ ɪt ǀ
And now some examples from real life:
But, yeah, at that point I thought, “My God, I could be much more charming than Hugh!” (Rupert Everett, BBC4).
And I should be very clear about the argument that I making about the role of veterans in this postwar groundswell (Kathleen Belew, BBC4).