prep2-105, 歧义的疑问？

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.

(A) by failing to honor its promise to its customers to keep  ??

(B) by its failure of honoring its promise to its customers to keep

(C) in its failing to honor its promise to its customers of keeping

(D) because of its failure in honoring its promise to its customers in keeping

(E) because of its failure to honor its promise to its customers of keeping

句子结构：Even though…, the state’ attorney general accused the bank of engaging in… by failing to…
                主语是attorney，谓语是accused，宾语是the bank，of engaging in…是介词短语作宾语补语。

考点：简洁有效、习惯用法

简洁有效，当because of, by doing, because, due to, by + 名词等在选项句首，第一选择是because连词，其次是by doing，因为动词比名词更能表达的意思更完整。

习惯用法，promise to do sth 或者promise that…

(A) 正确，by doing to do 表示engage in deceptive business practice 的方式；promise 的习惯用法是promise to do sth 或者promise that…，而不是promise of doing 或in doing sth。

(B) 名词failure 不如动词failing 简洁。

(C) its failing 是动名词不够简洁；promise of doing 的表达不正确。

(D) 名词failure 不如动词failing 简洁。

(E) its failing 是动名词不够简洁；promise of doing 的表达不正确。

我的问题是：A选项：by failing to 。。。  会不会有歧义认为是Attorney general 发出的动作？