D because it combines the sentences correctly. I think, I'm puzzled between d and a but I really do think its d. :) Hope this helps!
Answer:
it prepares them for what is going to happen
Explanation:
The thesis statement<span> is the sentence that states the main idea of a writing assignment and helps control the ideas within the paper. It is not merely a topic. It often reflects an opinion or judgment that a writer has made about a reading or personal experience.</span>
The poet creates a mood that is pessimistic
