铬是人体必需的微量元素，但铬过量会引起污染，危害人体健康。不同价态的铬毒性不一样，六价铬的毒性最大。下列叙述错误的是 （ ）
| A．K2Cr2O7可以还原乙醇，故可用来鉴别司机是否酒后驾驶 |
| B．污水中铬一般以Cr3+存在，与水中的溶解氧作用可被氧化为六价铬 |
| C．人体内六价铬超标，服用维生素C缓解毒性，说明维生素C具有还原性 |
| D．1mol Cr2O72－得到6mol电子时，还原产物是Cr3+ |
It’s high time you had your hair cut ; it’s getting _______ . 
| A．too much long | B．much too long |
C．long too much | D．too long much |
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 |