which　指代～～一直没搞明白啊！

先看两道题目～～

652.Since the movie was released seventeen UFOs have been sighted in the state, which is more than had been sighted in the past ten years together.
(A) which is more than had been sighted
(B) more than had been sighted
(C) more than they had sighted
(D) more than had reported sightings
(E) which is more than had reported sightings
the key:B
比较考点:省略主语

613.Sales of United States manufactured goods to nonindustrialized countries rose to $167 billion in 1992, which is 14 percent more than the previous year and largely offsets weak demand from Europe and Japan.
(A) which is 14 percent more than the previous year
(B) which is 14 percent higher than it was the previous year
(C) 14 percent higher than the previous year’s figure
(D) an amount that is 14 percent more than the previous year was
(E) an amount that is 14 percent higher than the previous year’s figure
the key:E
比较考点：比较对象。an amount ——the previous year’s figure

我知道在GMAT中which不可以代前面的整个句子，但在上面两个题目中，comma后的which都代的是前面的某个词（UFOs 和 167 million）但是答案中都没有出现which,想问下，是说comma后见到which指代就一定错吗？which指代一个词不用comma,除非是插入语吗？

好混乱啊～～请NN指点啊～～

因为GMAT 要求的是就近指代, 所以这里的which 指代只能是state ,以及1992. 

所以逻辑上是不成立.

comma后见到which指代就一定错吗？

comma后which紧跟修饰词就对（当然其它语法也要对）。你上面的例子中被修饰词都隔得老远的，老美那么笨，谁知道你指代谁。同时，语法都对的情况下，分词结构或者同位语比从句优。

做which题记住下面口诀： 有“ ，” 有 which , 没有“ ，” 没有which

如果选项中出现了没有带“，”的which， 那么直接排除

上面第一题which 虽然都带有“，” 不能直接排除，但which 这是只能指代离他最近的名字，即 state, 所以这时which 就错

第二题 本意也不是指代million,而是指the sales ... 因此也错

另外，which 再怎么也只是一个定语从句，如果出现了同位语，那么同位语比定语从句牛！