Birds' singing is sometimes a warning to other birds __________ away.
| A．to stay | B．staying |
| C．stayed | D．stay |
Many people are still in _____ habit of writing silly things in _____ public places.
| A．the;the | B．/; / | C．the; / | D．/; the |
What ______ public is concerned about is whether medical workers and scientists will be able to find for this new disease in a short time.
| A．不填;不填 | B．不填;the | C．the;不填 | D．the;a |
I smoke out of ____ habit, not for ____ pleasure; for I have been in the habit for twenty years.
| A．a; the | B．the; a | C．x; the | D．x; x |
The cakes are delicious. I’d like to have _______ third one as _______ second one I ate was too small.
| A．the, the | B．a, the | C．the, a | D．a, a |
In the market, vegetables are sold by _______ kilogram, I mean, by _______ weight.
| A．the; 不填 | B．不填; 不填 |
| C．the; the | D．不填；the |