下列四个数据都表示N2和H2合成氨的反应速率，其中速率代表同一反应中的是
① V(N2)=0.6mol/（L·min） ② V(NH3)=1.8mol/（L·min）
③ V(H2)=1.2mol/（L·min） ④ V(H2)=0.045mol/(L·s)
| A．①② | B．①③ | C．③④ | D．②④ |
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| 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 .
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| A．a; 不填 | B．the; 不填 | C．the; an | D．a ; the |
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| A．as a result of | B．on top of | C．in front of | D．in need of |