第二部分英语知识运用(共两节，满分35分)
第一节：单项填空(共15小题，每小题1分,满分15分)
从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21．While income worry is rather common problem of the aged, loneliness is another problem that aged parents may face
A．a; 不填 B．the；不填 C．a：the D．the，：the
22．The control and prevention of H1Nl is a big to China as well as the whole world．
A，surprise B．challenge C．reaction D．threat
