Hablar is a regular verb and ends in -ar, you use the vowel -e. that means that the 3rd person Indicative "habla" shifts to "hable."
Morphemic shift
When you get to regular -er and -ir verbs, they shift to vowel "a". For example, escribir is now escriba and escuchar is escuche.
It is often referred to as "the opposite vowel" since "a" shifts to "e" and "e" shifts to "a."
learn more about regular verbs in Spanish: https://brainly.com/question/7150507
