Answer: Option C. "Human Digestive Tract"
Step-by-step explanation:
Biological system is a network of living organism interact with each in a manner to maintain balance in the system.
Humans cover major part of biological system. The human digestive system is an important part of human body that consist of gastrointestinal tract along with the tongue, salivary glands, pancreas, liver, and gallbladder.
Human digestive tract or system functions in digestion of food that is responsible to provide energy to the body.
Biology textbook , the universe, and car engine are all non living organs.
Hence, human digestive tract is an example of biological system.