Answer:
nucleus and electrons
Explanation:
nucleus contains protons and neutrons
Atom, molecule , organelle, cell , tissue organ, organ systems, organism population, community, ecosystem, biome, biosphere
Answer:
While the digestive system collects and removes undigested solids, the excretory system filters compounds from the blood stream and collects them in urine. They are closely connected in controlling the amount of water in your body.
Explanation:
