We use can to express ability.
Can has only present and past forms.
Be able to is used for other aspects.
1. Abilities.
Dogs can swim, but they can't climb trees.Complete these sentences by putting can or can't in the correct place.
3. Questions and answers.
Write answers to the questions in the previous exercise.
Can dogs climb trees? No, they can't.For more information about ability and can see the Grammar Reference.