What genre best defines John Bunyan's Pilgrim's Progress based on this excerpt from the story? Now, as Christian was walking solitarily by himself, he espied one afar off, come crossing over the field to meet him; and their hap was to meet just as they were crossing the way of each other. The gentleman's name that met him was Mr. Worldly Wiseman, he dwelt in the town of Carnal Policy, a very great town, and also hard by from whence Christian came. This man, then, meeting with Christian, and having some inkling of him,—for Christian's setting forth from the City of Destruction was much noised abroad, not only in the town where he dwelt, but also it began to be the town talk in some other places,—Mr. Worldly Wiseman, therefore, having some guess of him, by beholding his laborious going, by observing his sighs and groans, and the like, began thus to enter into some talk with Christian.
A. fairytale
B. detective stories
C. allegory
D. adventure stories

An allegory is a story that points to a deeper meaning, idea or concept where the deeper meaning can be thought of as the moral of the story. The purpose of an allegory is to basically help the reader understand a deeper concept, not to mention that it also helps make your writing more interesting.

In this sense an allegory is very similar to a metaphor. They're different in a way, an allegory is a story that points to a deeper meaning whereas a metaphor is a more simple comparison.