用下列一种试剂就可鉴别出甲酸、乙酸、甲酸乙酯和乙酸甲酯, 该试剂是 （ ）
| A．银氨溶液 | B．新制Cu(OH)2悬浊液 | C．硫酸钠溶液 | D．氢氧化钠溶液 |
Encourage your children to try new things, but try not to ___ them too hard.
| A．draw | B．strike | C．rush | D．push |
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 |