Select the most appropriate option to fill in the blank and make a grammatically correct sentence.

There was a heated discussion ______ two members of the club.

between

The most appropriate option to fill in the blank is between.

The word "between" is used to refer to two things that are separate from each other. In the context of the sentence, there was a heated discussion between two members of the club, meaning that the discussion was between two specific people and not involving anyone else.

The other options are not as appropriate.

• Among is used to refer to a group of more than two things. This does not make sense in the context of the sentence, because there were only two members of the club involved in the discussion.
• Of is used to refer to a group of things that are considered together. This does not make sense in the context of the sentence, because the discussion was not between a group of things, it was between two specific people.
• In is used to refer to a place or space. This does not make sense in the context of the sentence, because the discussion was not taking place in a place or space, it was taking place between two people.