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

[ingolf]

English Error, Elementary Level

ESL/EFL Test #5 "Relative Pronouns", question 1

Whom is that sitting over there in the corner?

(a) Whom
(b) that
(c) there

English Error, Elementary Level

ESL/EFL Test #5 "Relative Pronouns", answer 1

Who is that sitting over there in the corner?

Correct entry: Who
The error was: (a) Whom
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Whom is that sitting over there in the corner?

Ingolf

[Yankee]

.
"Who is that sitting over there in the corner?" is the correct answer.

'Who' is the subject of this sentence. The objective form ('whom') cannot be used here.
.
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Amy
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ESL teacher, translator, and a native speaker of American English