Answer:
2. muscular system and cardiovascular system
I think the egg because it’s the start of their life cycle, or something. I don’t think the chicken came first bc the egg would be the baby and the chicken the adult.
Answer:
Protons,neutrons
Explanation:
Inside atom,the entire mass of it lies in nucleus.
So,we knew that mass of atom= no of protons+ no of neutrons
hence from we understand,nucleus contain both protons and neutrons