The best option for helping a reader determine how an author feels about a topic is D connotative. Connotative language includes words that carry emotional weight or associations beyond their literal meaning, which can reveal the author's attitudes and feelings toward the topic.
While the other options—A cause and effect structure, B single words, and C compare and contrast structure—can provide context and clarity, connotative language is specifically tied to the emotional undertones of the author's viewpoint.