What is the difference between "who" and "whom"?

[Monika Selesh]

ESL/EFL Test "Relative Pronoun Exercises", question 4

......... do you think would have a car like that?

(a) Whom
(b) That
(c) Who

ESL/EFL Test "Relative Pronoun Exercises", answer 4

Who do you think would have a car like that?

Correct answer: (c) Who

Your answer was: incorrect
Whom do you think would have a car like that?
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Why we used who and not whom here

[Alan]

Who is the subject of the sentence.
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English as a Second Language
You can read my ESL story Phrasal Verbs/hold