--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 |
China has promised to revise its existing regulations and ___ new policies according to WTO requirements.
| A．forming | B．to form | C．to be forming | D．have formed |
In the dream Peter saw himself ___ by a fierce wolf, and he woke suddenly with a start.
| A．chased | B．to be chased | C．be chased | D．having been chased |
___ the employees' working efficiency, the supervisor will allow them to have a coffee break.
| A．Improving | B．To improve | C．Having improved | D．Improved |
You can find whatever you need at the shopping centre, ___ is always busy at the weekend.
| A．that | B．where | C．what | D．which |
There are hundreds of visitors ___ in front of the Art Gallery to have a look at Van Gogh’s paintings.
| A．waited | B．to wait | C．waiting | D．wait |