31.The company had about 20 notebook computers but only one third _______used regularly . Now we have 60 working all day long.
| A．is | B．are | C．was | D．were |
He told me the news_____, believe it or not, he had earned $1 000 in a single day.
| A．that | B．which | C．as | D．because |
In that month, he earned as much as, if ____ than, $40 000.
| A．no more | B．not more | C．no much | D．not much |
The research is so designed that once _____ nothing can be done to change it.
| A．begins | B．having begun | C．beginning | D．begun |
If _____ carefully, the experiment will be successful.
| A．do | B．does | C．done | D．doing |
He is a man of few words, and seldom speaks until _____ to.
| A．spoken | B．speaking | C．speak | D．be spoken |