杀G新手上路，请教OG两道，OG12-10&OG12-14

luopite

本人现准备杀G一战，最近开始关注CD，发现此地潜伏着无数的NN。
今天开始看SC，从OG开始，详细看过OG的解释后仍有疑问，于是上CD来请教各位。才疏学浅，望不吝赐教。
og12-10.Carnivorous mammals can endure what would otherwise be lethal  levels of body heat because they have a heat-exchange network which kept the brain from getting too hot.
A.which kept
B.that keeps
C.which has kept
D.that has been keeping
E.having kept
答案是B，很容易选对。看过解释以后对which的用法产生了疑问。
八月上海XFD上课，老湿讲到：which不能指代一个句子，只能指代一个词，并且不能紧跟在所指代的名词后面，中间应该用逗号隔开；that指代名词的时候中间不需要用逗号隔开。
OG的解释：some writers follow the convention that which can only be used for nonrestrictive clauses, but insistence on this rule is controversial.
那我就不明白"can only be used for"是什么意思了，指的是只能引导非限定性从句吗？后面又加上一句这个说法有争议，那到底which的用法是什么呢？XDF老湿的说法有问题吗？求解答，已经有贴的话求给出链接。

og12-14.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 on 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，也不难选。问题是关于appear的。
个人觉得be和appear to be应该是有区别的，应该不能随意的变动，否则会改变原文的意思。那么appear和appear as是不是也有相同的问题呢？它们能不能等同于be呢？OG解释没有提到，求解答。

luopite

不会过很久了还没人理我吧……
希望各位赐教，不胜感激。

xiaoguolulu

啊，which不能紧跟在所指代的名词后面，有这样一个说法吗？那如果which只能引导非限制性定语从句的话，万一which前出现了好几个名词，那怎么知道which指代的是哪一个名词呢？which什么时候使用就近指代原则呢？

wuyw2010

which: 引导非限定性从句或介宾结构宾语
that: 引导非介宾结构名词

第二道答案是c

本人现准备杀G一战，最近开始关注CD，发现此地潜伏着无数的NN。
今天开始看SC，从OG开始，详细看过OG的解释后仍有疑问，于是上CD来请教各位。才疏学浅，望不吝赐教。
og12-10.Carnivorous mammals can endure what would otherwise be lethal  levels of body heat because they have a heat-exchange network which kept the brain from getting too hot.
A.which kept
B.that keeps
C.which has kept
D.that has been keeping
E.having kept
答案是B，很容易选对。看过解释以后对which的用法产生了疑问。
八月上海XFD上课，老湿讲到：which不能指代一个句子，只能指代一个词，并且不能紧跟在所指代的名词后面，中间应该用逗号隔开；that指代名词的时候中间不需要用逗号隔开。
OG的解释：some writers follow the convention that which can only be used for nonrestrictive clauses, but insistence on this rule is controversial.
那我就不明白"can only be used for"是什么意思了，指的是只能引导非限定性从句吗？后面又加上一句这个说法有争议，那到底which的用法是什么呢？XDF老湿的说法有问题吗？求解答，已经有贴的话求给出链接。

og12-14.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 on 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，也不难选。问题是关于appear的。
个人觉得be和appear to be应该是有区别的，应该不能随意的变动，否则会改变原文的意思。那么appear和appear as是不是也有相同的问题呢？它们能不能等同于be呢？OG解释没有提到，求解答。

-- by 会员 luopite (2010/9/18 19:14:11)

xiaoguolulu

啊，第二道明明选A啊~

luopite

第二道答案是C吗？
"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"。OG是这样解释的，有问题吗？

luopite

啊，which不能紧跟在所指代的名词后面，有这样一个说法吗？那如果which只能引导非限制性定语从句的话，万一which前出现了好几个名词，那怎么知道which指代的是哪一个名词呢？which什么时候使用就近指代原则呢？

-- by 会员 xiaoguolulu (2010/9/18 19:39:41)

一经提出，也有相同疑问