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题库 / Prep2007E2-SC-8
Ozone, a special form of oxygen that screens out harmful ultraviolet rays, reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.
has long appeared that it was immune from
has long appeared to have been immune from
has long appeared as being immune to
had long appeared immune to
had long appeared that it was immune to
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1. Ron: "immune from" means free of exempt from (eg. immune from prosecution), whereas "immune to" means not susceptible (eg. immune to chicken pox). In this case, the ozone layer was considered not susceptible to human influence. Thus, "immune to" is idiomatically correct.
2.在we have now realized已经是现在完成，意味着在过去某个时间点之前我们都以为ozone是 immune from human influence，自然应该用过去完成时态。
3. it appeared后面加从句it blah blah是redundant，appear作为系动词，后面可以直接加形容词做表语。这样最为简洁清楚。
E和D的差别在于D更简洁，逻辑链更清晰。appear作为系动词可以直接接形容词，为啥要it形式主语+appear that+it代词一起上阵来表意呢？只会让表意效果打折扣，逻辑链纠在一起不顺畅。
Know your tenses:
Have/has = present perfect (started in the past and continues until now)
Had = past perfect (happened before another event in the past)
1. You need a past tense in order to use the past perfect (I had studied for three years before I took my GMAT).
2. The usage of past and present perfect tenses could work, but again, you need a simple past to say when something started in the past (I had studied for three years before I took my GMAT, but since then I have not wanted to study).
3. The biggest error in the sentence (I have received a high score in GMAT because I had prepared hard for it" is wrong) is meaning: receiving a high score is a one time event (past) not a continuing event (present perfect).
immune to； immune from，前者是对···免疫；后者是免除于····；排除AB；
as being immune to 这种说法太wordy了，GMAT要求语言简练，直接排除C；类似的题目还有很多；
剩下DE；
seem，appear，look，feel，smell，sound，taste是系动词，后面可以直接跟形容词；D很简洁又正确；
immune to； immune from，前者是对···免疫；后者是免除于····+注意时态是过去完成时
The verb tense in the underlined part of the sentence must be compared with what is taking place now. As the sentence states we have realized that emissions of industrial chloroflorocarbons deplete the ozone layer (present perfect), we need the past perfect had appeared to indicate a time period prior to the present. Additionally, "immune from" means free of exempt from (eg. immune from prosecution), whereas "immune to" means not susceptible (eg. immune to chicken pox). In this case, the ozone layer was considered not susceptible to human influence. Thus, "immune to" is idiomatically correct.
E is too wordy. "appeared immune" is just fine on its own. Notice that we have "it appeared immune." The "it" here refers to the ozone. Thus, to say: "it appeared that it was immune" would be unnecessary.
"immute to... 不受...影响; immune from... 免除… 排除AB
seem, appear, look，feel, smell, sound, taste是系动词，可以替换成be动词，直接接形容词
E 第一个it形式主语，第二it臭氧，代指不同错误
C 时态不正确，时态应该比have now realized早"
时态错了，选了has been
ron：the past time is implied in the context -- it's whenever we made the discovery that human activities can affect the ozone layer.
b选项：has appeared的时态就错了，不用考虑后买呢to have been immune了；后面说现在意识到的情况，那么前面就是过去的情况
it appears that …it作形式主语 但这里的it是有明确对象的
immute to... 不受...影响; immune from... 免除...
seem, appear, look，feel, smell, sound, taste是系动词，可以替换成be动词，直接接形容词
E appear不及物
AD 差异：.immute to... 不受...影响; immune from... 免除...
appear 表现得，类似于be， 后面加表语，那么AE就不对
BC的been与appear是重复的，所以不对
appear是表语，后面需要补语
没有搞清意思，后文用的是现在完成时，前边的内容发生在之前所以应该用过去完成时
可以用it appears that，但是在it做形式主语时，如：
It appears that there has been a mistake. 看来有一个差错。
It appears unlikely that interest rates will fall further. 看来利率不大会再降低。
；虽然可以连接两个独立句，但含分号的句子依然是一个句子而不是两个。
The ozone had appeared immune, but now we have realized……。had表示在我们意识到某事之前，人们不是这么看它的。
seem, appear, look，feel, smell, sound, taste是系动词，可以替换成be动词，直接接形容词；同时，系动词没有被动式，不管人还是物发起都用主动式，如：it tastes good; it appears nice.
1.immute to... 不受...影响
immune from... 免除...
"immune from" means free of exempt from (eg. immune from prosecution), whereas "immune to" means not susceptible (eg. immune to chicken pox).
2.在we have now realized已经是现在完成，意味着在过去某个时间点之前我们都以为ozone是 immune from human influence，自然应该用过去完成时态。
3. it appeared后面加从句it blah blah是redundant，appear作为系动词，后面可以直接加形容词做表语。这样最为简洁清楚。
1. 时态上，AE都有错，主句has／had appeared，后面从句was，就是错误的。这里从句应该与主语时态是一致的。
2 在we have now realized已经是现在完成，意味着在过去某个时间点之前我们都以为ozone是 immune from human influence，自然应该用过去完成时态。
3. it appeared后面加从句it blah blah是redundant，appear作为系动词，后面可以直接加形容词做表语。这样最为简洁清楚。
E： 无论第一个it 是形式主语还是代表ozone都不对 - appear 是系动词后加表语，所以不用再加it
A臭氧对人类影响免疫这件事情在地球上空被显示出来；D臭氧在地球上空对人类影响免疫
语意，D更优