We ________ take clean drinking water for granted. One day we may run out of it.
| A．needn't | B．can't |
| C．won't | D．shouldn't |
Young people go to college with the expectation that______educated people get a higher pay.
| A．good | B．better | C．best | D．the best |
Only when Tom fully recovered______back to work.
| A．did he go | B．he went | C．had he gone | D．he had gone |
The couple finally bought the house they wanted, for they______enough money.
| A．had saved | B．were saving | C．would save | D．were to save |
You look so tired. You______have stayed up late again.
| A．should | B．can | C．may | D．must |
－ Has Tom already finished his new story?
－ I Have no idea. He______it last month.
| A．had written | B．was writing | C．would write | D．wrote |