二、单项填空（本节有10小题，每小题1分，共10分）
21. Many people agree that ______ knowledge of English is a must in ______ international trade today.
| A．a; 不填 | B．the; an | C．the; the | D．不填; the |
All the students ______ gets along very well with will be invited to her birthday party．
| A．who | B．that | C．she | D．what |
Some old Chinese customs, many of you are too young to know, have already died out．
| A．what | B．that | C．how | D．as |
Whether ways will be found to stop pollution or not is just _______ worries the public．
| A．why | B．which | C．that | D．what |
It’s necessary to be prepared for a job interview．___ the answers ready will be of great help．
| A．To have had | B．Having had | C．Have | D．Having |
Not far from the house ____ two gardens, ______ seated nearby playing bridge with his children．
| A．were; whose owner | B．was; of which the owner |
| C．were; its owner | D．was; owner of which |