/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).
This is the type of work I do with my students in my one-to-one classes. I make them practise these processes with exercises until they improve their comprehension of native speakers and are capable of speaking like that themselves. If you are interested in my classes, you can contact me here.