According to the Cambridge Dictionary, exhaustive means "complete and including everything". With that definition, it should not be gradeable: something can be complete or not complete, but it can't be very complete or too complete. What that means is that we should not be able to use adverbs of degree line too and enough with exhaustive.
Having said that, this NGram graph shows that we do often use too exhaustive. It is clear than in some of the examples I checked, the writer actually meant too exhausted, but there were also credible examples where the meaning was correct, for example this one:
A respected appellate judge writes, “ My experience teaches ... that too few law review articles prove helpful in appellate decision making. They tend to be too talky, too unselective in separating the relevant from the irrelevant, too exhaustive." - Legal reasoning and Legal writing, Richard K. Neumann 2005
When we use enough as a determiner, it goes before a noun:
Do you have enough money to pay the rent?
When we use an adverb to qualify an adjective, the adverb normally goes before the adjective. As the "Words and phrases that go before and after adjectives" section in this article explains, there is one notable exception- enough, which always follows the adjective it modifies. Here is an example:
This tea isn't sweet enough.
When we use too to qualify an adjective, it follows the rules, and always goes before the adjective.
This tea is too sweet.
In your sentence, the words are being used as adverbs to qualify an adjective, and the blank spaces are before adjectives. The third option (enough) does not work in either position, but the other two are OK. Reading the question again, it does state that two of the options are acceptable.
- Is it too exhaustive or not exhaustive? -
- Is it too exhaustive or not too exhaustive?