The difference in
hardness between diamond and graphite is that diamond has an ordered
arrangement of atoms within its structure that makes it harder and stronger
than graphite. This is due to the high pressure and high temperature that it
went.
Answer :
(A) The balanced chemical reaction will be:

This reaction is a single replacement reaction.
(B) The balanced chemical reaction will be:
This reaction is a double displacement reaction.
(C) The balanced chemical reaction will be:

This reaction is a combination reaction.
Explanation :
Balanced chemical reaction : It is defined as the reaction in which the number of atoms of an element present on reactant side must be equal to the product side.
Part (A):
The balanced chemical reaction will be:

This reaction is a single replacement reaction in which the most reactive element displaces the least reactive element from its solution.
Part (B):
The balanced chemical reaction will be:

This reaction is a double displacement reaction in which a positive cation and a negative anion of two reactants exchange their places to form two new products.
Part (C):
The balanced chemical reaction will be:

This reaction is a combination reaction in which the two atoms combine to form a larger molecule.
Find the average of these 2 temperatures, since they have the same volume.
(80 + 10) ÷ 2 = 90 ÷ 2 = 45°C
You can only use this method of averaging them out because they have the same volumes :)
I think the answer is A but I’m not 100% sure