He stepped into the office, down and began to work at once. A. sitting B. to sit C. hav——青夏教育精英家教网—

摘要： He stepped into the office, down and began to work at once. A. sitting B. to sit C. having sat D. sat [解析]选D.分析句子结构可知.空格部分在句中作并列谓语.故用sat.

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He stepped into the office, _______ down and began to work at once．