题目

The Bunsen Burner is so named because it is thought ___________ by Robert Bunsen.   A. to be invented               B. having been invented   C. invented                     D. to have been invented 答案：D 解析: 本句考查动词的被动语态和时态，it+is+动词ed形式，to do是固定的搭配用法。而Bunsen Burner的发明是过去发生的动作，所以用完成时态。

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