The young couple, who returned my lost wallet, left ______I could ask for their names.
| A．while | B．before | C．after | D．since |
______ is known to us is that tobacco contains nicotine and other harmful products, so you should give up smoking.
| A．As | B．It | C．What | D．Which |
This book is considered to be the best novel of its kind ever.
| A．to write | B．writing | C．having written | D．written |
-- I can’t find my umbrella.
-- I saw George going away with____, but I’m not sure whether it is yours.
| A．it | B．that | C．one | D．the one |
I can't _him in the knowledge of wild plants．As a matter of fact, he' s an expert．
| A．match | B．win | C．compare | D．defeat |
It's years we met each other at a party in Qingdao .
| A．when | B．that | C．before | D．since |