Scientistshave recently found evidence that black holes probably existat the core of nearly all galaxies and the mass of each black hole isproportional to its host galaxy.og19的792题
1）例如: A do sth. than (do) B，如果是主语A和B进行比较，在没有歧义的情况下可以省略do, 但如果sth.会和B有一类事物的风险，可以补充do用以说明是两个主语的比较，或者当时态出现变化时，也需要补充do（do, did等形式）
eg. Fewer people will enter the labor force in the 1980’s than (people) did in 1970’s.
2）如果谓宾都相同的话，谓宾也可以省略
eg. A study found that women who took new jobs after retiring from their primary careers reported high marital satisfaction, more than those who retired completely (reported high martial satisfaction). 可以看到比较的是women （who引导的定语）和另一类women（who引导的定语）作比较，补充了比较对象，对于相同的谓宾就可以省略了，也并不会有歧义
3）如果比较的是同一事物的不同状态，需要加上those/that，后面跟上不同状态的引导词（时间、归属等等）
eg. company’s earnings in the first quarter were more than double THOSE of the previous quarter.
因为单纯比较in the first quarter和the previous quarter，省略those的话，默认补充完整的句子是company's earning in the first quarter were more than double (company's earning in the first quarter) of the previous quarter. 明显的歧义，所以要用those指代company's earning后面加上比较的时间. PS.关于完全和不完全指代they/those的区别建议看看曼哈顿
4）比较从句的主语和谓语与主句的主语和谓语相同时，可以全部省去，常常保留做状语的介词短语和状语从句
eg. In no other historical sighting did H’ comet cause such worldwide sensation as (HC caused a sensation) in its return of 1910 – 1911 倒装句，还原回来是HC did cause such worldwide sensation IN no other historical sighting as (HC did cause such worldwide sensation) In its return of 1910-1911
另外看你这个问题
Scientists have recently found evidence that black holes—regions of space in which matter is so concentrated and the pull of gravity so powerful that nothing, not even light, can emerge from them—probably exist at the core of nearly all galaxies and the mass of each black hole is proportional to its host galaxy.
很明显，比较对象应该是每个black hole的质量是所属银河质量的一部分，是句子的主语进行比较。单从C选项来看，两个比较对象是mass of each black hole和its host galaxy作比较，比较对象不一致。如果说省略的话，那么省略的部分要在前面找出来，也就是主句的主语，抄写下来则变成：
Scientists have recently found evidence that black holes exist at the core of nearly all galaxies, and that the mass of each black hole is proportional to (the mass of each black hole) its host galaxy.
就是说如果要省略，必须找到完全一样的东西才能省略，比较对象是mass of black hole和mass of its host galaxy, 前面并没有出现mass of its host galaxy, 所以不能随便省略，需要用代词that不完全指代前面的mass，就变成that of its host galaxy.
谢谢gong，我看到其他答主拿ron的例子句子，我觉得特别好。分享一下（https://forum.chasedream.com/thread-955830-1-1.html）
。我现在感觉省略不能算是一种严格意义的语法，在比较中的省略其实有严格的平行规则，看起来很像省略，但其实不是，是一种平行。
比较中的省略：
a) Oil prices in 2007 were higher than those in 2008.
noun+modifier vs. noun+modifier
b) Oil prices were higher in 2007 than in 2008.
adv. vs. adv.
c) Oil prices were higher in 2007 than oil prices in 2008.
d) The weather is hot and dry in Nevada, as it is in Arizona.
sentence vs. sentence
e) As in Arizona, the weather is hot and dry in Nevada.
adv. vs. adv.
注意：Ron说no “omissions”，b) c) d) e)都算是omission，但是在比较结构中，b) d) e)都正确，而c)错误。
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发表于 2019-11-24 11:02:29
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