The government must take measures to prevent the river __________.
| A．polluted | B．polluting |
| C．from polluted | D．being polluted |
In the past twenty years great changes _______in China.
| A．were taken place | B．have been taken place |
| C．have taken place | D．were happened |
The old city wall ______ in the Ming Dynasty.
| A．was been built | B．has been built | C．was built | D．had been built |
The doctors have done ______ they could ______the child.
| A．whatever; to save | B．everything ; save |
| C．all what; to save | D．all which; save |
The teacher asked the students ______ .
| A．how did that come about | B．how that came about |
| C．that how this came about | D．how that was happened |
I don’t know where I ______ my dictionary, which cost me 50 yuan.
| A．have lied | B．had lain | C．have laid | D．have laid |