It's fused into natural mixes by autotrophs and enters the dirt when living beings die.
Answer:
Explanation:
Option 4 bescause theres 4 extra cell and they are haploid.
The immune system, and the excretory system
(Honestly, all of them work to keep us 'healthy', but I believe these are the ones you're looking for)
A. Order, Arrangement, world and Universe