Question

Did you see (who,whom) that was?
choose who or whom?

Answer 1

Who
Did you see who that was

Answer 2

Both: "whom" is grammatically correct but "who" is generally used

Step-by-step explanation:

The word "who" is used to represent or ask about the subject, while "whom" is used for the object. In this case, "you" is the subject, "see" is the verb, and "who/whom" is the object. Therefore, only "whom" is strictly correct.

Now, however, a lot of people only use the word "who", and the use of "whom" is generally considered as posh or snobbish. So I'd recommend using "whom" if it's a homework assignment, and "who" in day-to-day life, but you can use "whom" too.