It is "to whom". You use whom as an object and whoas a subject, just as you use him as an object and heas a subject, or me as an object and I as a subject. This gives you an easy way to check whether you should use who or whom: try substituting he or him, or I or me.
For example, would you say "give it to he" or "give it to him"? Since "give it to him" is correct, you know that you need to use an object after "to", so that tells you to use "whom". You could also have used "give it to me" or "give it to I" to tell you the same thing: "give it to me" is correct, showing that you need an object after "to".
D.O. is what or whom I.O. is to whom or for whom
Yes, "whom" can be the object of a preposition (for whom, with whom, of whom, etc.).
Give the letter to Mary. to whom?The letter is for Mary. for whom?
whom
It is spelt "whom". It is the objective form of "who".
To whom it may concern Who is a subject pronoun; it is used as the subject of a verb. Whom is an object pronoun. If you find you can replace who/whom with he, she, or they, who is correct. If you find you've replaced who/whom with him, her, or them, then whom is correct.
with whom
for whom?
Con quien means "with whom"
With whom did she go with? Whom I did not like very much. I wouldn't be suprised at whom he ran away with.
"Whom" is not a substitute for "who", it's another case. "Who" is the Nominative, while "whom" is either the Dative or the Accusative.To whom do we owe this pleasure?Whom have you told so far?The girl whom I saw yesterday is her sister.
by whom binary is invented