（ ）是整个教学工作的中心环节，是提高教学质量的关键。

(单选题)47.（ ） (单选题)46.（ ） (单选题)—Could you do me a favor and take these files to my office?— (单选题)My friends went there to watch the barriers ______ by the po (单选题)We spent several days ______ all related reference materials (单选题)______ we persist in carrying out the open-door policy, we w (单选题)He seldom smokes, ______? (单选题)I propose you ______ finish this project as soon as possible (单选题)Tom was ______ to tell the truth even to his parents. (单选题)Lucy got a promotion in her company, ______ was a big surpri