500℃、20MPa时，将H2和N2置于一容积为2L的密闭容器中发生反应反应过程中H2、N2和NH3物质的量变化如下图所示，下列说法正确的是
| A．反应开始到第一次平衡时，N2的平均反应速率为0.005 mol/(L·min) |
| B．从曲线可以看出，反应进行到10min至20min时可能是使用了催化剂 |
| C．从曲线可以看出，反应进行至25min时，增加了0.1mol氨气 |
| D．在25min平衡正向移动但达到新平衡后NH3的体积分数比原平衡小 |
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 |