19世纪中叶，俄国化学家门捷列夫的突出贡献是（ ）
| A．提出原子学说 | B．发现元素周期律 | C．提出分子学说 | D．发现氧气 |
My friend showed me round the town, ______ was very kind of him. 
| A．which | B．that | C．where | D．it |
They use computers to keep the traffic _______ smoothly.
| A．being run | B．run | C．to run | D．running |
If you leave the club, you will not be_____back in .
| A．received | B．admitted | C．turned | D．moved |
What I need is_____ book that contains ______ABC of oil painting.
| A．a; 不填 | B．the; 不填 | C．the; an | D．a ; the |
Jenny nearly missed the flight______ doing too much shopping.
| A．as a result of | B．on top of | C．in front of | D．in need of |