Which of the following statements are true about stem-changing verbs? Check all that apply.

A: Only -er and -ir verbs are stem-changing verbs.

B: they have the stem changes in all conjugations except for nosotros and vosotros

C: Their stems only change in the singular conjugations.

D: They use the same endings as regular -ar, -er, and -ir verbs if they are regular verbs.

E: stem changing verbs can change their stems from e-ei, e-i, o-ue, or u-ue.

F: stem changing verbs use the regular -ar and -er verb endings, but not the -ir verb endings.