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 |