Choose the appropriate verb forms to complete the sentences. 1. He said he (can't/couldn't) couldn't afford to buy that expensive watch. 2.1 am sure John (will/would) in biology. get a satisfactory mark 3. It's no use (going/to go) prove that they are not to blame. there. You won't be able to 4. I (has always been looking/am always looking) forward to (participating/participate) in such concerts. 5. Christopher Columbus (was/has been) known explorer. a well- 6. How (does this mechanism usually function/is this mechanism usually functioning) 7. Do you know why Silvia (has refused/is refused). to apologize? 8. I will be very much surprised if Mr Langley (will succeed/suc- ceeds) in finishing this job. 9. If Boris (prevents/will prevent) departure, we will be really happy. Uncle Jacob's 10. Sarah (has been used/has been using) these devices since