对比两道OG语法题,望牛人指教~

OG(11e)第9题

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

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答案是A. OG在讲选项C的时候只是说,although通常只引导一个句子.

另有一题,是OG-Verbal当中的第18题

With only 5 percent of the world's population, United States citizens consume 28 percent of tis nonrenewable resources, drive more than one-third of its automobiles, and use 21 times more water per capita than Europeans do.

(A) With

(B) As

(C) Being

(D) Despite having

(E) Although accounting for

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答案是E.

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这两处是否矛盾呢?

另外,顺便问一下,on和at的区别重要么?LZM的语法改错精解里提到on后面是面,at后面是点或线.

望牛人指教,谢谢!

第二题中的although引导从句用了省略形式而已