SAT English Practice Question

The author's use of the word "but" in this sentence creates a contrast between two ideas, one about the way humans communicate and one about the way other animals communicate. The sentence suggests that humans are more likely to use complex language than other animals are. What is the most likely reason why the writer uses the word "but" in this sentence?

1. A.create a sense of urgency and excitement.
2. B.introduce a comparison between two contrasting ideas.
3. C.emphasize the importance of the speaker’s message.
4. D.suggest that the speaker is addressing a large audience.