In english:

in the preterite tense, verbs that end in -car, -gar, -zar must make a change in the of the stem before adding this change is only done in the form.

verbs that end in -zar must change the to a before adding the ending of

verbs that end in -car must change the to a before adding the ending of

verbs that end in -gar must change the to a before adding the ending of