There are 3 types of atoms in an ammonia solution, NH4OH: nitrogen, hydrogen and oxygen. So, your answer in this context is A.
However, if you were considering just ammonia on its own (NH3) there are only two types of atoms, nitrogen and hydrogen.
The one with the highest pH would be a solution with 100 mL of water and also 20 mL of 0.1 M NaOH is added. Solutions without buffers would have the highest pH since the resistance to change is very low. Hope this answers the question.
Dark colored moths survived better in the Industrial Revolution because their dark color helped them camouflage in soot. When the industrial revolution ended there wasn't as much soot, so the light colored moths now had a better chance of survival.
Explanation:
A point of temperature at which both solid and liquid state of a substance remains in equilibrium without any change in temperature then this temperature is known as melting point.
For example, melting point of water is 
. So, at this temperature solid state of water and liquid state are present in equilibrium with each other.
Therefore, when a 100 g of given pure metal in solid state is heated at its exact melting point which is 
then some of the solid will change into liquid state but the temperature will remains the same.
