(2007全国Ⅱ12)At the beginning of class,the noise of desks ______ could be heard outside the classroom.
A.opened and closed B.to be opened and closed
C.being opened and closed D.to open and close
答案:C
解析:考查非谓语动词。过去分词作定语表完成、被动;不定式作定语表将来;现在分词作定语表示正在进行。由句意可知开关课桌的动作正在进行,因此用现在分词被动式作定语。
句意:开始上课时,开关课桌的声音在教室外面都能听到。