Present Tense: ask, laugh, decide, learn
Past Tense: asked, laughed, decided, learned
With Be: She is pleased with her new car.
With Be and Have: She has been offered another position.
To introduce infinitives:
I used to work for Pat.
To modify or describe nouns:
I bought a used refrigerator.
Present: I walk
Past: I walked
Future: I will walk
Present Perfect: I have walked
Past Perfect: I had walked
Future Perfect: I will have walked