下列描述中正确的是（ ）
| A．氯水是纯净物，氯水中的次氯酸具有杀菌消毒作用 |
| B．加碘食盐中所加的“碘”一般是碘化钾 |
| C．氢氧化铁胶体可以使混浊的水变澄清，可作水的消毒剂 |
| D．漂白粉的有效成分是次氯酸钙 |
The computer was used in teaching. As a result, not only__________, but students became more interested in the lessons. 
| A．saved was teachers’ energy | B．was teachers’ energy saved |
C．teachers’ energy was saved | D．was saved teachers’ energy |
The children all turned ____ the famous actress as she entered the classroom. 
| A．looked at | B．to look at |
C．to looking at | D．look at |
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 |