A.
Physical change
Step by step explanation;:)
A tornado! I think or it could be rain
<h2>

</h2>
Explanation:
1. Water decomposition
- Decomposition reactions are represented by-
The general equation: AB → A + B.
- Various methods used in the decomposition of water are -
- Electrolysis
- Photoelectrochemical water splitting
- Thermal decomposition of water
- Photocatalytic water splitting
- Water decomposition is the chemical reaction in which water is broken down giving oxygen and hydrogen.
- The chemical equation will be -

Hence, balancing the equation we need to add a coefficient of 2 in front of
on right-hand-side of the equation and 2 in front of
on left-hand-side of the equation.
∴The balanced equation is -
→ 
2. Formation of ammonia
- The formation of ammonia is by reacting nitrogen gas and hydrogen gas.
→ 
Hence, for balancing equation we need to add a coefficient of 3 in front of hydrogen and 2 in front of ammonia.
∴The balanced chemical equation for the formation of ammonia gas is as follows -
→
.
- When 6 moles of
react with 6 moles of
4 moles of ammonia are produced.
Endothermic or C, if you would like a reason why, do not hestitate to ask
I would say diamond, because it consists only of carbon