You should avoid...

1) concise language
2) specific, concrete nouns
3) phrases like true fact, close proximity, cooperate together, and basic
essentials.
4) All of the above
5. None of the above

#1 is incorrect because concise language involves using to-the-point, non-fluff language and vocabulary to get one's ideas across--this is obviously necessary for effective writing.

#2 is incorrect because concrete nouns are simply physical nouns that aren't abstract, such as "I", "You", "Michael", "Table", "Cat".  Concrete nouns are obviously used effectively in writing constantly.

#3 is incorrect because these expressions are formal rather than informal and will therefore fit well into most academic writing.

#5 None of the above is therefore correct.

an old person

explanation:

lemme actually be useful and say i believe the answer is the first one.