Akeyword is used to replace a. hard to spell words c. words written backwards b. confusing words or phrases d. all of these

The answer is the letter B as the definition of a keyword in this context is: A keyword is a familiar word used to replace an unfamiliar or difficult word or concept.

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.

the answer is culture