In his victory speech ________before a huge crowd of his supporters，Obama declared that “change has come to America”．
| A．having delivered | B．to be delivered |
| C．delivering | D．delivered |
They are still very cautious about ________ side effect the new medicine will bring about, although the experts have tried it on about 2000 patients．
| A．which | B．that | C．where | D．what |
His opinion was such a good one _________ his family all agreed to accept．
| A．which | B．and | C．that | D．as |
_____ is known to us all that the 2012 Olympic Games will take place in London．
| A．It | B．Which | C．As | D．What |
_______ on your study, and you will make greater progress．
| A．Concentrating | B．If you concentrate |
| C．Concentrate | D．To concentrate |
—Would you give it another guess?
—____ —tell me the answer．
| A．Let me think | B．You never know |
| C．Never mind | D．I give up |