Question

owls eat small vertebrates, including mice and birds. there are some parts of an owls food, including bones and fur, which the owl cannot digest. many owls regurgitate, or spit up, some of the waste left over from their food. this regurgitated waste is called a pellet. this photograph shows bones inside an owls waste pellet. an owls ____ removes waste that contains fur and bones from the owls prey. digestive system excretory system

Explanation:

The digestive system is responsible for processing food. Since the text mentions that owls cannot digest parts like bones and fur (which are part of the food intake), and they regurgitate (a digestive - system related process) the waste (pellet) containing these indigestible parts. The excretory system is mainly for removing liquid waste (like urine in mammals, though birds have a different excretory product - uric acid). But here, the process of getting rid of indigestible food parts (bones and fur from prey) is related to the digestive system.

Answer:

digestive system