The answer to the question stated above is <span>an unknown antecedent.</span>
Weak reference:
when a pronoun refers to an antecedent that has been suggested but not expressed
Indefinite reference:
the use of a pronoun that refers to no particular person or thing and which is not necessary to the meaning and structure of a sentence
Answer: Channels
Explanation: they are used to convey messages (you can think of it as a road that takes you where you want to go)
It's A as to the avoiding double negation which is not possible in English.