在高温、高压和催化剂条件下的密闭容器中，进行反应：N2(g)+3H2(g)
2NH3(g)，下列有关说法不正确的是（ ）
| A．达到平衡时，正反应速率等于逆反应速率 | B．增大氢气的浓度可增大反应速率 |
| C．在上述条件下，氢气能全部转化为氨气 | D．达到平衡时，体系中各物质的浓度不再改变 |
Edward, you play so well. But I ______ you played the piano. 
| A．didn’t know | B．hadn’t known |
C．don’t know | D．haven’t known |
She brought with her three friends, none of ______ I had ever met before. 
| A．them | B．who | C．whom | D．these |
I tried phoning her office, but I couldn’t _______. 
| A．get along | B．get on | C．get to | D．get through |
His sister left home in 1998, and _______since. 
| A．had not been heard of | B．has not been heard of |
C．had not heard of | D．has not heard of |
What do you mean, there are only ten tickets? There _____ be twelve
| A．should | B．would |
C．will | D．shall |