In a chemical reaction, atoms are rearranged to form new molecules. However, atoms are neither created nor destroyed.

What happens to the total mass of the atoms involved in a chemical reaction?
A.
It will decrease if two molecules combine to form a single compound.
B.
It will increase if a new compound is formed during the reaction.
C.
It always changes as the atoms are rearranged into new molecules.
D.
It will stay the same no matter how the atoms are rearranged.