Answer:
The choice that best adds specific and concrete detail to the vague phrase seemed very dark in the passage is B) seemed black and murky.
Step-by-step explanation:
Choice B) seemed black and murky is the correct option because these two adjectives describe water in a much more detailed way. By introducing these two specific and concrete characteristics, readers can create a better image in their minds because these adjectives appeal to their senses in a more specific way.