※ 引述《sunny86 (勿忘初衷！)》之铭言：
: 题目：
: We regret _______ your office of the changes to the program earlier and
: apologize for any inconvenience this may have caused.
: (A) to inform
: (B) not having informed
: (C) not to inform
: (D) the informing of
: 疑问：为什么是B而不是A
以下为我的看法，仅供参考，有误请指正，谢谢。
We regret _______ your office (of the changes to the program earlier)
‘and’(apologize for any inconvenience) this may have caused.
()省略后，变成
We regret _______ your office‘and’this may have caused
^^^^^^^^^^^^^^^^ ^^^^^ ^^^^^^^^^^^^^^^
and为对等连接词，前后词性、动态要一致，答案就出来了 have +PP ^^"
然后因为regard后面可以加 to RV. 、 Ving、 that子句...
所以就是B了