OG12-14

我觉得是visible和appear的区别吧。appear表示to come into sight,有个动态的过程。不对的话请更正

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
(E) appear as dark spots on the Sun’s surface, which have never been sighted on
答案是A,OG针对C的解释是：Although typically intriduce a subordinate clause, which has a subject and a verb, but here there is no suject and sighted is not a complete verb

跟人觉得，虽然这个从句没有主语，但由于sighted是过去分词，其主语等于主句主语。这样的话，这个从句就不需要主语了，不是吗？

谢谢

状语从句的省略形式，在句尾优先修饰就近动词的主语，这里就成了修饰同位语vortices of gas 。只有状语从句在句首，其逻辑主语等于句子主语。如果这种状语从句耳朵省略形式出现在句尾要注意那些就近的动词（分词）。