31. A warm thought suddenly came to me _______ I might use the pocket money to buy some flowers for my mother’s birthday.
| A．if | B．when | C．that | D．which |
Tom, behave yourself! If you keep on doing that, you'll ____ in serious trouble.
| A．shut up | B．end up | C．take up | D．pick up |
I would like to buy some good English reference books, but _______ was available from the bookstore, where I only found some Chinese ones.
| A．nothing | B．no one | C．none | D．neither |
Everybody has _____ responsibility to save water, if future generations are to enjoy
____ similar standard of living to the one we enjoy now.
| A．the; / | B．a; a | C．/; the | D．a; the |
— Do you know when he ________ the trip to the USA?
— Perhaps next week, but I’m not sure.
| A．makes | B．made | C．has made | D．is making |
My sister is determined. ________ she has made up her mind, nothing can change it.
| A．Though | B．Once | C．Unless | D．Until |