化学在日常生活和生产中有着重要的应用。下列说法不正确的是（ ）
| A．明矾水解形成的Al（OH）3胶体能吸附水中悬浮物，可用于水的净化 |
| B．纯二氧化硅大量用于制造光导纤维 |
| C．Al2O3的熔点很高，可用于制作耐高温材料 |
| D．电解MgCl2饱和溶液，可制得金属镁 |
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 |
Could I speak to ______ is in charge of International Sales please?
| A．who | B．what |
| C．whoever | D．whatever |