The solution for exercise 4 in chapter 11B - Experiences or things? of English File Elementary - Student's Book by Christina Latham-Koenig, Clive Oxenden and Jerry Lambert
Question
Look at ten verbs which take the infinitive. Which one is irregular? Which one can be regular or irregular?
Complete the sentences with a verb from a in the past tense.
Answer
a)
Forget is irregular (forgot).
Learn can be regular or irregular (learned / learnt).