Final answer:
Regressive Assimilation is when a sound changes due to the influence of a following sound. In the word 'conference,' pronouncing the /n/ labiodentally due to an upcoming /f/ is an example of this type of assimilation.
Step-by-step explanation:
Producing the first /n/ in "conference" labiodentally is an example of Regressive Assimilation. Assimilation in phonetics is a process by which a sound becomes more like a neighboring sound in terms of one or more of its phonetic characteristics. In the case of regressive assimilation, also known as right-to-left or anticipatory assimilation, a sound is modified due to the influence of a following sound. So, in the word "conference," when the /n/ is pronounced using the lips, like a labiodental sound, due to the influence of the /f/ which is a labiodental sound, it's an example of regressive assimilation.