Use of “that” or “the” with the title “option A”

Question

Context: I volunteer with a student who is taking the CELPIP exam in Canada. In this exam they give a survey with two options (option A and option B). The student has to choose an option and say why he/she thinks it's the best.

My student wrote the following:

I think the option A is the best because ... (sounds wrong to me)

As a native speaker, I suggested that he use either of the following:

1. I think that option A is the best because...
2. I think option A is the best because...

My question is why do we use “that” or no article before "option A"?

Also, why can we say “I think that the best option” or “I think the second option is the best”?

Answer 1

Option A already has a determiner: "A". It's like a proper noun: it refers to one and only one thing, so it can't have another determiner. It's already as determined as can possibly be. You only need articles (or other determiners, like "some", "that", "this", etc.) to resolve the inherent ambiguity of common nouns, which by definition can refer to any instance or instances of the concept that they denote.*

The same principle is at work in video games that refer to "player one" and "player two" with no article (the number is the determiner), "apartment 3G", "room 222", etc.

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That is usually optional when it's a subordinating conjunction:

Greg told us that he'll be late.
Greg told us he'll be late.
George likes to pretend that he's an architect.
George likes to pretend he's an architect.

It's not optional as a demonstrative adjective or pronoun:

I choose that option.
I want that back.

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* _{There are, of course, some proper nouns with articles, like The United States and The Dardanelles and formerly The Ukraine. These usually have a "conceit" that they are somehow determining a common noun, pointing out a particular instance. Note that many are plural.}