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
答案是C， 问为什么A，D不行？ be visible as这个结构错吗？ 还是完成时大时态有问题？C中的altough never sighted是不是省略了什么？哪位给讲讲结构吧， 谢谢！
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发表于 2004-3-13 17:58:00
