In this section, we will briefly describe possible ways of reducing the costs and risks __________ in doing this.
| A．involving |
| B．involved |
| C．to involve |
| D．being involved |
The last half of the nineteenth century _____ the steady improvement in the meansof travel.
| A．has witnessed | B．was witnessed | C．witnessed | D．is witnessed |
Once environment damage _____, it takes many years for the system to recover.
| A．has done | B．is to do | C．does | D．is done |
As _____ announced in today's papers, the Shanghai Export Commoditiser Fair is also openon Sunday.
| A．being | B．is | C．to be | D．been |
–It must have been lots of fun riding round in a car.
–Yes, you know this was the first time that _____ round in my own car.
| A．I rode | B．I should have ridden |
| C．I’ve been riding | D．I’d ridden |
Until then, his family _____ from him for six months.
| A．didn't hear | B．hasn't been hearing |
| C．hasn't heard | D．hadn't heard |