Answer:
Phonology
Explanation:
Phonology is the unit of language in sound. It is the study of sounds, production, and the audition and the perception of the sound. This operates at the sound level. To know the sound of a word is basically very little to know about the sound. One word can be changed in other words by changing its sounds.
Thus here Lauren held a conversation with her mother. To understand the sound of adult Lauren have to understand the sounds, speech, and production. And this category comes under phonology.