Distinguished guests and friends, welcome to our school. the ceremony of the 50th Anniversary this morning are our alumni（校友） from home and abroad.
| A．Attend | B．To attend | C．Attending | D．Having attended |
Nancy enjoyed herself so much she visited her friends in Sydney last year.
| A．that |
| B．which |
| C．when |
| D．where |
______the Internet is of great help, I don’t think it’s a good idea to spend too much time on it.
| A．If |
| B．While |
| C．Because |
| D．As |
It is difficult for us to learn a lesson in life______we’ve actually had that lesson.
| A．until |
| B．after |
| C．since |
| D．when |
“You can’t have this football back_____you promise not to kick it at my cat again.” the old man said firmly.
| A．because |
| B．since |
| C．when |
| D．until |
environmental damage is done, it takes many years for the ecosystem（生态系统）to recover.
| A．Even if |
| B．If only |
| C．While |
| D．Once |