Mr. Smith ______ the grammar book meant for senior high school students and will almost finish it.
| A．was writing | B．has written | C．has been writing | D．has been written |
By the time he realizes he __________ into a trap, it'll be too late for him to do anything about it.
| A．walks | B．walked |
| C．has walked | D．had walked |
He __________ football regularly for many years when he was young.
| A．was playing | B．played |
| C．has played | D．had played |
Though we don't know what was discussed, yet we can feel the topic __________.
| A．had changed | B．will change |
| C．was changed | D．has been changed |
—What is the price of petrol these days?
—Oh, it __________ sharply since last month.
| A．is raised | B．has risen |
| C．has arisen | D．is increased |
—Why does the lake smell terrible?
—Because large quantities of water __________.
| A．have polluted | B．is being polluted |
| C．has been polluted | D．have been polluted |