第一部分语言知识运用
第一节 单项填空（共15小题，每小题1分，满分15分）
21．We work together to achieve our common purpose： world that is safer cleaner and healthier than one we found．
| A．the；the | B．a；不填 | C．a；the | D．the；不填 |
Someone is at the door, who is ?
| A．this | B．that | C．it | D．he |
.In the United States, bus travel doesn't cost much as train travel, ?
| A．don't they | B．does it | C．do they | D．doesn't it |
is very clear to everyone that he's round and tall like a tree.
| A．This | B．What | C．That | D．It |
Many people now make a rule to buy cards for their friends before Christmas.
| A．themselves | B．it | C．that | D．this |
I think it a great honour to visit your country.
| A．to invite | B．inviting | C．having invited | D．to be invited |