To fully comprehend a novel, you usually have to understand the in which it is set and written. plot geography context genre

The correct answer is Context.  A lot of information in written material is given between the lines, therefore, we need to understand not only the actual words but all that surrounds the story as intention and the unspoken words which are in fact, the context

By definition, a plot is the series of events that one after another creates the story so this word doesn't make any sense in the sentence.

The geography in a novel can give us a lot of information about the kind of life the characters would have even though it is not necessary to know it to understand a story.

The genre could be necessary to be understood if we're going to make a deep analysis of the novel but not to understand it.