4. _____ can be done _____ been done.
I don't have enough money.I, _____, can't afford to buy Audi A3 Sportback.
Where was it ______ you _______ our maths teacher?
----- Mary looks very upset. She _______ failed to pass the exam. ----- I guess so. It's very difficult after all.
— When could you have a meal with me? — I'd like to go ___ it is convenient to you.
— Who are you going to have _______ this letter for you? — My secretary.