چرا فکر میکنید در موقعیت رسمی فقط میشه از یه حالت استفاده کرد در حالیکه هر دو حالت زیر از لحاظ گرامری درست هستند و هر دو هم formal محسوب میشن؟!
...whom I spoke to... (formal)
...with whom I spoke... (formal)
در ضمن، منبع مشکلی نداره. magoosh یه سایت و شرکت معروف آمریکاییه که در زمینه آمادگی آزمونهای معتبر زبان انگلیسی فعالیت میکنه.
ولی اگه بیشتر به مثال های دیکشنری علاقه مند هستید، شما رو ارجاع میدم به مطلب زیر در دیکشنری وبستر:
whom /ˈhuːm/ pronoun
Learner's definition of WHOM
—
used in formal writing or speech
-
To whom am I speaking?
-
His brother, with whom he is very close, works for the same company.
-
I was introduced to the artist, whom I was anxious to meet.
-
an author whom I had never heard of
Usage Whom is a more formal word than who and is not commonly used in ordinary speech and writing, where it can seem awkward and unnatural.
-
(formal) To whom did you speak? = (formal) Whom did you speak to? = (more commonly) Who did you speak to?
-
(formal) We weren't sure whom to hire. = (more commonly) We weren't sure who to hire.
-
(formal) The person to whom we spoke was very helpful. = (formal) The person whom we spoke to was very helpful. = (more commonly) The person who/that we spoke to was very helpful.
-
(formal) Her brother, whom I met last year, is an attorney. = (more commonly) Her brother, who I met last year, is an attorney.