Be Able To Exercises

Be able to is used when "can" or "could" cannot express the full meaning. Since "can" only has present and past forms (can/could), we need "be able to" for other tenses: "I will be able to help you tomorrow" (future), "I have been able to work from home this year" (present perfect), and "She wants to be able to drive" (infinitive after another verb). After other modals, use "be able to" because two modals cannot go together: "You might be able to come" (not "You might can come").

For past ability, there is an important difference between "could" and "was/were able to." Could describes general ability — something you could do at any time: "I could swim when I was young." Was/were able to describes a specific achievement on one occasion: "After two hours, the rescue team were able to reach the climbers" (they succeeded in a specific situation). You cannot use "could" here. However, in negative sentences, both work: "I couldn't find my keys" = "I wasn't able to find my keys." This distinction between general and specific past ability is frequently tested in Cambridge B2 First and C1 Advanced examinations.