B1/B2 ability in the present and past

Modal auxiliaries - what are they? Well, words like can, could, may, might, would, shall, etc. And the problem is that they are defective. What does that mean? Well, they're not like other verbs. They don't have an infinitive, or they don't have a past participle form. Now, that means that if we're talking about can, well, what are we going to do if we want to use can as an infinitive, or as a past participle? Well, what we have to do is to look for another verb, which has a similar meaning. ...