What will people die of in 100 years? If you think that is a simple question, you ______ attention to the revolution taking place in biotechnology．
| A．have not been paying | B．had not been paying |
| C．were not paying | D．will not be paying |
—I don’t mind telling you what I know.
—You _____. I can manage it myself.
| A．mustn’t | B．ought not to | C．can’t | D．don't have to |
The decorations were so lovely that they _____ in a short time.
| A．sold out | B．has been sold out | C．were sold out | D．were selling out |
The students _____ are hard-working and ready to help others should be praised.
| A．who | B．whom | C．which | D．whose |
—What’s the noise outside?
—Some children_____ hide-and-seek in the yard.
| A．were playing | B．are playing | C．have played | D．played |
I couldn’t help feeling greatI put on the parachute and was pulled off the beach.
| A．even though | B．whether | C．while | D．the moment |