Which of the following is an osmotic regulatory challenge that a fish living in salt water faces?

salt expulsion
urea expulsion
uric acid expulsion
water expulsion

Sea water has a very high salt concentration. Therefore salt expulsion is the biggest challenge as the salts have to move against a concentration gradient (from a low concentration to a high concentration.)

The return of the wolf to yellowstone national park will probably affect the bird population to some degree, not significantly. while wolves will hunt birds when necessary, they prefer to hunt larger prey. the bird population will most likely only be affected when hunting is scarce for the wolves. birds of prey will also probably not be affected as much as other birds who spend more time on the ground hunting for food as the tend to spend more time in the air or in trees since they do not need to stay on the ground for long due to the nature of the way they hunt.