X、Y为短周期元素，X位于ⅠA族，X与Y可形成化合物X2Y，下列说法正确的是
| A．X的原子半径一定大于Y的原子半径 |
| B．X与Y的简单离子不可能具有相同的电子层结构 |
| C．两元素形成的化合物中，原子个数比不可能为1∶1 |
| D．X2Y可能是离子化合物，也可能是共价化合物 |
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 |