分类：教育/科学-外语学习
问题：请问怎么选择?谢谢！WHY？149.Electronsarekn 
9. Electrons are known _____ continuously.  A. moving  B. being moved  C. to be moving  D. to be moved
回答：选C。to be moving

known to be moving，被（人）知道是不断地运转的。