Since he was only a little boy,the policeman had to let him leave_____A unpunished B being punished C unpunishing D having been unpunished 为什么不能用D?

Since he was only a little boy,the policeman had to let him leave_____
A unpunished B being punished C unpunishing D having been unpunished
为什么不能用D?

D 是现在分词的完成式,表示的是已经发生的事情,这里通过意思,犹豫他只是个小男孩,警察不得不不做任何惩罚就放他走.这里在当时句子的语境来说不是已经发生的事情,所以不能选D.