3. 解析：选B。keep out the cold 不要让凉气进来。keep off不使……接近，使避开；keep out of不让进入……，后接名词，表示范围。

2.解析：选C。第一个President作同位语，表头衔，不用冠词。第二个空作宾语，指总统本人，用定冠词。

5. Both; worried

提升练习

3. as4. would rather

2. was heading towards; without

6. made the decision

3. take in4. In addition5. say again

B. 1. keep back2. kept3. kept; from

4. keep off5. keep; out

C. 1. connected with2. at once

10.Building

7. abnormal8. leadership9. rare