第21题: [单项选择](),the guest spealer was ushered into the auditorium hall to give the lecture A. Being shown around the campus B. Having shown to the campus C. After been shown around thecampus D. Having been shown around the campus 参考答案:D 答案解析:
be shown around the campus 这一动作发生在was ushered in to the auditorium hall 之前, 故应用完成时的被动语态