Conjugate the verb preferir in all forms in the Present Tense. What takes place in the conjugation that makes this verb a stem-changing verb?

The verb preferir is a stem-changing verb in the Present Tense, specifically in the second and third person singular and third person plural forms. The stem change occurs in the e of the stem.

Here are the conjugations of preferir in the Present Tense:

- Yo prefiero (I prefer)
- Tú prefieres (You prefer)
- Él/ella/usted prefiere (He/she/you [formal] prefer)
- Nosotros/as preferimos (We prefer)
- Vosotros/as preferís (You all prefer)
- Ellos/ellas/ustedes prefieren (They/you all [formal] prefer)

The stem change takes place in the e, which changes to ie in the second and third person singular and third person plural forms.