de选错d
明显d更简洁
e
where it had long appeared that it was immune to 啰嗦

E，where it had long appeared that it was immune from human influence;
第一个it是形式主语，是臭氧层对人类的影响免疫这件事显现了出来，不是臭氧层显现出来臭氧层对人类的影响免疫

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

错选B

You don't need an actual past-tense verb. You just need a clear indicator of a definite point in the past——the point that serves as the point of view for "had ___ed".

如果把第一个it当做形式主语，则两个it指代不一致 错

AE where后的第一个it指ozone，that后的it也指ozone，说了两遍主语 错
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.
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

B tohavedone ，todo不定式的过去时，太冗长了，和前面的had appear重复，而且主要是前面的时态错

时态，have realized 已经发生，所以realize发生在过去，所以前句appear应该是过去的过去had long

appear as thebeing 错

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).

过去的某个时间点有错误认知，但是看后句就知道现在已经不是了，所以不用现在完成时

考时态

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.

AE的it与前面的形式主语的it指代冲突排除
B中appear to后的have been immune from的have been与前面的has long重复
C没有appear as being这种用法
Dhad done很好的表现了分号前后句子的时间关系 。

immute to... 不受...影响
immune from... 免除...

当然牙牙的immune from和to的区别要加进去座位第四点，就完美了。

调研了下，总结
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。

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.