49. 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
(E) which doubles to twelve the number of satellites now known that orbit
The pronoun which should be used to refer to a previously mentioned noun, not to the idea expressed in an entire clause. In A, C, and E, which seems to refer to a vague concept invol¬ving the detection of moons, but there is no specific noun, such as detection, to which it can refer. Also in E, the use of the phrasing the number... now known that orbit is ungrammatical and unclear. B and D use the correct participial form, doubling, to modify the preceding clause, but D, like A, uses known as orbiting rather than known to orbit, a phrase that is more idiomatic in context. B, therefore, is the best answer.
不明白og对这里which的使用的解释,难道它的意思是说不能指代句子,只能指代名词么?另外,如果有一个名词可以被指代,从上下文意思来看,应该是什么词呢?
谢谢