Cells, tree, digestive system, public transportation system, government systems, school systems, families, dog, forest, pond, prairie, communication systems, towns, insect, solar system, weather systems, bird, correctional system, squirrel, soil, etc.
Answer: C
Explanation: All organisms someway somehow must compete for essential resources.
Answer
B: by turning on a battery-powered radio to hear music
Nucleus is the answer
Hope this helps :D