Choisir is a french second group verb. So it follow the regular conjugation pattern of the second group like:
finir. Follow this link to see all the endings of the conjugation of the second group verbs :
conjugation rules and endings for the second group verbs.
Choisir is conjugated the same way that verbs that end in :
-ir.
The prototypical verb for the second conjugation is
finir. The conjugation is, marked by the vowel
i and the infix
-iss- in the indicative present and imperfect.