※ 引述《sunny86 (勿忘初衷！)》之銘言：
: 題目：
: 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
: 疑問：為甚麼是B而不是A
以下為我的看法，僅供參考，有誤請指正，謝謝。
We regret _______ your office (of the changes to the program earlier)
『and』(apologize for any inconvenience) this may have caused.
()省略後，變成
We regret _______ your office『and』this may have caused
^^^^^^^^^^^^^^^^ ^^^^^ ^^^^^^^^^^^^^^^
and為對等連接詞，前後詞性、動態要一致，答案就出來了 have +PP ^^"
然後因為regard後面可以加 to RV. 、 Ving、 that子句...
所以就是B了