What is the main reason you should know the meaning of every word in a short story as opposed to a novel?
a) the vocabulary tends to be more challlenging in a short story than in a novel.
b) the language in short stories is denser than the language in a novel.
c) short stories include more symbolic messages than novels do.
d) teachers are more apt to test you on a short story than a novel.

Either B or C could apply, but I would say the best choice is C. Word choice is extremely important in short stories because the authors have to exercise "word economy", which basically means that since they have a limit on the maximum amount of words the can use, (because it's a short story) they have to pay close attention to which specific words they use, and the connotations of those words. Symbols are really significant in many short stories because they can illustrate deep meaning without using extensive metaphors and situations.