Inferred is another word of saying "taken to perspective" or "interpreted as...".
Hidden meanings or messages are meant to be figured out and used to help you in future situations.
So, I would say:
a. True!
Technically, all of these answers are ways to revise your work. I would go with B, Run a spell check and correct errors because it looks like the most accurate way to edit documents.
The correct answer is A.<span>could not be heard above the voices in the hallway
</span>
B is a subject, C is an adverbial of reason, while D is an adverbial of manner.
