Final answer:
The correct entry is a. Crumb, R., illustrator. Bob and Harv's Comics. By Harvey Pekar, Running Press, 1996, which aligns with MLA citation style.
Step-by-step explanation:
The correct works-cited entry to use for a comic written by Harvey Pekar and illustrated by R. Crumb, in an essay comparing the work of R. Crumb to the work of other illustrators, is option a. Crumb, R., illustrator. Bob and Harv's Comics.
By Harvey Pekar, Running Press, 1996. This format highlights the role of R. Crumb as an illustrator, which is pertinent to the focus of the essay, and it conforms to the Modern Language Association (MLA) citation style guidelines for emphasizing a contributor's role when relevant to the discussion.