【过去分词单选】英语高手进Though ________ of danger,sightseers have been

【过去分词单选】英语高手进Though ________ of danger,sightseers have been flocking(簇拥)
Though ________ of danger,sightseers have been flocking(簇拥) to the site where the world's biggestterrorist Bin Laden lived.
A.warned
B.warning
C.being warned
D.having warned
为什么不能选择C
though 是连词,可以连接俩个谓语动词啊
有人说前半句是省略了sighteers are的省略句 是如何看出的哪?