OG11第71题

The cameras of the Voyager II spacecraft detected six small, previously unseen moons circling Uranus, which doubles to twelve the number of satellites now known as orbiting the distant planet.

(A) which doubles to twelve the number of satellites now known as orbiting

(B) doubling to twelve the number of satellites now known to orbit

(C) which doubles to twelve the number of satellites now known in orbit around

(D) doubling to twelve the number of satellites now known as orbiting（B）

(E) which doubles to twelve the number of satellites now known that orbit

请问：书中说用分词doubling可以指代前面整个clause，所以可以选B。可是我的理解是用doubling的话，其逻辑主语不是camera么？用which才可以指代前面整个句子吧？

可是现在分词在其他时候都是由主句主语为动作发出者的，这次怎么一下子就说指代整个句子了？