______ is said that our math teacher often does volunteer work on weekends.
| A．One | B．This | C．It | D．That |
I took the wrong train _______. I didn’t even know it until half an hour later .
| A．by mistakes | B．by mistake |
| C．with mistake | D．with mistakes |
The mobile phone has influenced people’s life a lot since it ________.
| A．invents | B．invented |
| C．is invented | D．was invented |
--- I have trouble _______ my new computer.
---Don’t worry. I’ll show you how _______it.
| A．using; using | B．to use; to use |
| C．using; to use | D．to use; using |
–Do the Smiths live next to you? --No, but they____.
| A．used to | B．used to do it |
| C．used to be | D．used |