<span>D) Vaccines allow for building immunity without harmful exposure because not all viruses are safe to be exposed to.</span>
For there privacy you never know
Nitrogen (N) and Oxygen (O)
The chemical formula is N_2O
Answer: because its a chemical
Explanation: i dont know for sure but here is my theroy the animls eat it and it goes through out the ecosystem i dont want to get into to much detail but it can spread bc its a chemical it has a atomic number of 6