Answer:
Vocabulary.
Explanation: To compare two literary texts, it is essential to find out the similarities and differences which both the texts have in common. characters are the most important element while comparing two texts as their character traits and representation would offer the basis to compare. Then, style also is crucial while comparing as if we compare two writers having two distinct writing styles as each writer chooses a particular style to emphasize the message they want to convey to the audience, it would propose a better clarity of thoughts. For say, if an expository text is compared to a narrative text, certain differences in manner of portrayal of similar issue in different frames could be witnessed. Comparison of themes would help the readers to go beyond the description and illuminate their critical-thinking. While vocabulary is also significant as it could help to know the author's purpose behind usage of some words. yet among all these vocabulary seems less significant as the other three are the major elements of comparison.