Which statement is true about stem-changing verbs in the preterit?
a: Only -ir stem-changing show a stem-change in the preterit
b: All stem-changing verbs show a stem-change in the preterit
c: No stem changing verbs show a stem-change in the preterit
d: Stem-changing verbs in the preterit normally change 0 ---> ue or e ---> ie