.
Playing with a cell phone, he suddenly ________ the teacher staring at him.
| A．knew of | B．became aware of |
| C．reflected | D．aware for |
Shortly after the accident, two＿＿＿police were sent to the spot to keep order．
| A．dozen of | B．dozens | C．dozen | D．dozens of |
These tables and desks are all made of＿＿＿＿＿．
| A．a wood | B．some wood | C．the wood | D．wood |
Jumping out of＿＿＿＿＿airplane at ten thousand feet is quite＿＿＿＿＿exciting experience．
| A．不填； the | B．不填； an | C．an； an | D．the； the |
The warmth of＿＿＿sweater will of course be determined by the sort of＿＿＿wool used．
| A．the； the | B．the；／ | C．／； the | D．／；／ |
Paper money was in＿＿＿use in China when Marco Polo visited the country in＿＿＿thirteenth century．
| A．the；／ | B．the； the | C．／； the | D．／；／ |