Answer: I would go with B.
Explanation: The group of words for option B seem like they would be used more for contrasting than option D. It can't be option A or option C because those options use comparing signal words.
Answer:
I'd say fact
Explanation:
It's a claim being made by a nutrition expert, who is someone who has studied that subject and would be a reliable source.
Answer:
The stream floods easily during a rainstorm and is muddy.