There is a crowd of people in front of the house over there. 那边的房子前面有一群人.
What do you suppose__A___ there? 你认为那里发生了什么?
A.has happened (完成时) B.happening动名词形式不符合该句子 C is happened 被动态显然不合适 D.to have happened 不定式形式不符合该句子