______ at the door before entering please.
| A．Knocked | B．Knock | C．Knocking | D．To knock |
I asked her _____ have to study before I could go to university.
| A．how long would I | B．how soon would I |
| C．how long I would | D．how soon I would |
_____ surprised me most was to see so many people waiting for my arrival.
| A．That | B．It | C．Which | D．What |
--- Why did you call the police?
--- I got home and found my house _____.
| A．broken up | B．broken down | C．broken in | D．broken out |
The government has taken some measures to prevent more trees from _____.
| A．cutting down | B．cut down. |
| C．being cut down | D．been cut down |
Susan, _____ university student from Europe, teaches me _____ art in her spare time.
| A．an; / | B．a; the | C．an; the | D．a; / |