Answer:
Here you go.
Explanation:
First of all, there are reactants and products…
Reactants are in the left side (in bold).
Products are on the right (without bold)
Example; NH3 + O2 → N2 + H2O
4) would be your correct answer
Every 2 million years the amount is halved
0 million = 200g
2 million = 200g/2 = 100g
4 million = 100g/2 = 50g
1. Decreases by 4. (B)
2. The atomic number changes. (B)
3. 56/26 Fe. (C)
4. Potassium-40;t1/2=25 days. (B)
5. Takes place in the upper atmosphere. (A)
