The listens to disclosure.
a. channel
b. message
c. receiver
d. source

The correct answer is c. receiver.  The receiver listens to disclosure.

In this sentence we are presented with a communicative situation and the options are the elements of this situation. In a normal communicative situation we would have a source that wants to transmit some information to another person. The source then emits a codified message carying that information through a communicative channel that finally reaches the receiver, who then interprets the message.

In the mentioned sentence, the verb "listens" is describing the action performed by the receiver of the message, who is listening to the disclosure.

the purpose of the heading in the passage is to identify who is telling the story.

this excerpt is part of the book sugar changed the world (2010) written by marc aronson and marina budhos. as the book has been written by two people, the heading "marc" indicates that this specific excerpt is being narrated by aronson. in the fragment, marc describes his grandfather's story after hearing it from his cousin. however, there are other excerpts where budhos is the one that tells the story of her family.

aronson and budhos, who are husband and wife in real life, decided to write sugar changed the world when they found out how sugar, which had an important role in slavery and economy, changed their ancestors' lives.

well if u read the book you would know that she meant to