OR12 SC 14

s

Sunspots, vortices of gas associated with strong electromagnetic activity, are visible as dark spots on the suiface 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 ar
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

答案说C和D错在although后的句子不完整，但是它的主语是SUNSPOTS，和主句主语一致， 是不是可以省略阿？

xiongbaobao

主语+be……，although…… 在这种结构当中although后面重复的主语和be可以省但是C D谓语是appear因此although后面的主语不能省

s

谢谢