Which, out of the two statement below, is grammatically correct? Iago manipulates Othello throughout the play, as opposed to being the worthy...

When is it grammatically correct to use
who and when whom should be used instead often
intrigues all of us. In informal speech the word of choice is usually who, and people
only tend to consider the rules of grammar that govern the usage of these words in
formal speech or edited prose.

There are several relatively
simple rules that can be used to determine which of the two should be used. I have
provided one of them.

Who is a subjective pronoun and whom
is in the objective case. Determine the correct word to use by substituting with he/she
or him/her. If you can apply the former use who, else use
whom.

For example: Mike was the person who scored the
winning point. ("He scored the winning point." not "Him scored the winning
point.")

On the other hand: It was Joe whom  I saw in the
park yesterday. ("I saw him in the park." not "I saw he in the
park.")

Now let's look at the sentences you have
provided:

readability="11">

Iago manipulates Othello throughout the play, as
opposed to being the worthy friend whom Othello believes he
is.

Iago manipulates Othello throughout the play, as
opposed to being the worthy friend who Othello believes he
is.

Using the rule provided
earlier it would be right to say "Othello believes in him," not "Othello believes in
he." So the correct form is whom.