---Why is the classroom so dirty? --- Sorry, sir. It ______ yesterday. We forgot to do it.
---How long may I _____________ the book? ---Two weeks.
These aren’t my keys. Mine ___________ in the drawer.
The old man is too tired _________ go any further.
His father is __________ engineer and he works __________ research.
---Which would you like to eat, bread or sandwiches? ---___________. Please give me some dumplings.