Which of the following statements are true about irregular verbs? Check all that apply.

1. Their yo forms all end in -oy rather than the -o of regular verbs.

2. They follow the standard conjugation rules except in the singular first (yo) and third (él/ella) persons.

3. They do not follow the conjugation patterns of regular -ar, -er, and -ir verbs.

4. The Stem of their conjugated forms may look very different from their infinitive forms.