Final answer:
The third person singular form of the verb "servir" doesn't take a stem change.
Step-by-step explanation:
The form of the verb "servir" that doesn't take a stem change is the third person singular. In this form, the verb remains in its regular stem of "serv-" without any changes. For example, in present tense, "él or ella sirve" (he or she serves) does not have a stem change. However, in other forms such as first person singular, first person plural, and third person plural, the verb does undergo a stem change.
Learn more about Spanish verb conjugation