1.by 指的是以...方式，逻辑不符，排除AB
2.fail to do; the failure to do, 排除D
3. fail “in” ..... 后面跟失败的领域，范畴，活动； 意思是 “在....地方失败“

AD区分：
横线前的句子是“州检察长指控该银行从事欺诈性商业行为”，这里控诉已经表明是因为“欺诈商业行为”了，不需要再用because of来说明因果，而是应该是其他介宾短语作定语说明是什么欺诈行为。所以DE不对。
failure of 后面跟失败的对象，通常是名词，比如 the failure of the company，the failure of this slave rebellion，极少有跟动名词的情况，如果一定表示失败的具体行为，to do 是更好的选择。
failure in 后面跟失败的所属的领域、范筹、活动等，比如failure in the exam, failure in the interview，明显与题目语义不符。
failure to do 表示失败的具体行为，没有做到的事情，如果要跟动词，to do 是最好的选项。
所以B不对
in和by，这里介宾短语作定语是要翻译介词的，by“通过”比in"在之中"更合适，C排除

the failure to honor promises WAS the deceptive business practice. 而不是failure to keep promises 导致了deceptive business，故DE错误

【转自RON及KMF大神】
two things:
(1) incorrect idiom: \'promise of keeping\' is wrong. the correct form is \'promise to keep\'.
(2) change in meaning: the correct meaning is what appears in the original sentence, namely, that the failure to honor promises WAS the deceptive business practice. choice e, with its use of \'because\', implies that the failure to keep promises LED TO (other) deceptive business

DE改变了句意：
正确的意思是：原句：failure to honor promises本身是deceptive business practice
而E选项用了because之后，句意变为：failure to keep promises 导致了deceptive business

"这里的by是表示engage的方式
fail to do
promise to sb to do承诺某人做某事
"

promise in / of keeping are just not idiomatic=> "promise to its customers to keep" is the correct version. This leaves us with A and B.

大家都说这里用by不用because，是因为银行守信失败是银行参与欺骗性商业行为的方式，不是原因。但是为什么不能理解为银行守信失败是律师控告的原因呢？修饰前面半句话？

引用
two things:
(1) incorrect idiom: \'promise of keeping\' is wrong. the correct form is \'promise to keep\'.
(2) change in meaning: the correct meaning is what appears in the original sentence, namely, that the failure to honor promises WAS the deceptive business practice. choice e, with its use of \'because\', implies that the failure to keep promises LED TO (other) deceptive business

归因：规则生疏
B of错 C地点状语 in错
DE 主句结构变了，跟原句意思不符，而且accuse of 后面已经是原因了，没必要再说一次原因，而且两个原因还不一样
A其实也不太好，by后加上its failing 表意才正确，因为介词by后的动名词在这里是做名词的，名词没有发出者
不过再重申一遍，verbal没有完美选项，相对合理即可

1. idiom promise sb to do sth
2. AB选项，by doing sth这里修饰的都是就近的动词，A：by failing to do...句意完整；B：抽取核心词by its failure 只提到了失败，句意不完整，比较之下选A

promise to sb to do sth

idiom: promise to sb. promise to do sth.

不能是通过/因为 failure失败

C: in doing表示在做某事的过程中做了某事，通常in前面的动作是后面动作的一部分，比如另一例句：I solved all the problems in OG12 in preparing for the GMAT.无论修饰哪个名词都说不通。
D: failure in 和 promise in 都不对
E: promise in keeping is not idiomatic and the 'stacked' prepositions is just awful

A：tim "by failing" modifies "engaging". i don't like it either, but again, the GMAT makes the rules.. :)
E: 'promise of keeping' is wrong. promise of + (real) noun or promise to do
摘：failure of 后面跟失败的对象，通常是名词，比如 the failure of the company，the failure of this slave rebellion，极少有跟动名词的情况，如果一定表示失败的具体行为，to do 是更好的选择；failure in 后面跟失败的所属的领域、范筹、活动等，比如failure in the exam, failure in the interview

deceptive business practices 这里控诉已经表明是因为“欺诈商业行为”了，不需要再用because of来说明因果

根据绝对确定的点进行排出。

change in meaning: the correct meaning is what appears in the original sentence, namely, that the failure to honor promises WAS the deceptive business practice. choice e, with its use of 'because', implies that the failure to keep promises LED TO (other) deceptive business practices.

Even though it was not illegal for the bank to share its customers' personal and financial information with an outside marketing company in return for a commission on sales, the state's attorney general accused the bank of engaging in deceptive business practices by failing to honor its promise to its customers to keep records private.

AD区分：
横线前的句子是“州检察长指控该银行从事欺诈性商业行为”，这里控诉已经表明是因为“欺诈商业行为”了，不需要再用because of来说明因果，而是应该是其他介宾短语作定语说明是什么欺诈行为。所以DE不对。
failure of 后面跟失败的对象，通常是名词，比如 the failure of the company，the failure of this slave rebellion，极少有跟动名词的情况，如果一定表示失败的具体行为，to do 是更好的选择。
failure in 后面跟失败的所属的领域、范筹、活动等，比如failure in the exam, failure in the interview，明显与题目语义不符。
failure to do 表示失败的具体行为，没有做到的事情，如果要跟动词，to do 是最好的选项。
所以B不对
in和by，这里介宾短语作定语是要翻译介词的，by“通过”比in"在之中"更合适，C排除