CR蓝皮书的几道语法题，请大家赐教呀

xiaoyu612

Sunspots , vortices of gas associated with strong electro-magnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun's poles or equator.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 never been sighted on
这道题做了至少有四遍了，但每次都错，而且错的都是不一样的答案，不明白为什么要选用介词AT而不是ON，还是说这道题跟选介词哪个没关系，为什么不能用ARE VISIBLE 而选了APPEAR，同样不明白
答案是C

清飞扬

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清飞扬

建议LZ以后看到having been done和done这两点比较，直接把having been done的选项排了，不管是面对although, after等等的连接词，having xxxx正确的情况目前我只做到过一道就是having需要3个平行

babybearmm

同学，这哪来的书？答案错了，这题选A
这是OG12 Question 14......建议直接下载电子版og吧

C结构就错了，og解释是：
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.

Sunspots , vortices of gas associated with strong electro-magnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun's poles or equator.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 never been sighted on
这道题做了至少有四遍了，但每次都错，而且错的都是不一样的答案，不明白为什么要选用介词AT而不是ON，还是说这道题跟选介词哪个没关系，为什么不能用ARE VISIBLE 而选了APPEAR，同样不明白
答案是C

-- by 会员 xiaoyu612 (2012/2/1 3:03:11)

babybearmm

并不是肉眼可见才叫visible

肉眼可见  visible to the naked eyes

什么借助显微镜、望远镜能看到的，都叫做visible
Cells are visible with microscope.

这里"are visible"的表达perfect，用"appear"反而不好。这是学术英语，讲究精确性严密性，我是很少看到scientific papers里面有用"appear"，除非真的要说“看起来就仿佛像.....”