[求助][讨论]大全和OG11答案不一样的一道题

chenyudie

大全677

        Sunspots, vortices of gas associated with strong electromagnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun’s poles or equator.

(A) are visible as dark spots on the surface of the Sun but have never been sighted on

(B) are visible as dark spots that never have been sighted on the surface of the Sun

(C) appear on the surface of the Sun as dark spots although never sighted at

(D) appear as dark spots on the surface of the Sun, although never having been sighted at（C）

(E) appear as dark spots on the Sun’s surface, which have never been sighted on

 

大全上给的答案是C，XDF黄皮书上也给的是C，但是OG11上给的答案是A     指出C.Although typically introduces a subordinate clause, which has a subject and a verb, but here there is no subject and sighted is not a complete verb

 

不明白C为什么不可以是状语从句省略，省了sunspots are???

mbz

A is correct, and forget about C