How does osmoregulation take place in trout fish?

The gills actively uptake salt from the environment by the use of mitochondria-rich cells. some marine fish, like sharks, have adopted a different, efficient mechanism to conserve water, osmoregulation. they retain urea in their blood in relatively higher concentration.

Explanation:

well for one plants are always the producer, so a is the answer. a wolf is more of the consumer(predator) and the deer is the prey so i know those two are out of the question. also mushrooms are fungi/fungus so a is the producer.