What is always true, according to the law and conservation of matter

A new molecules cannot be formed from the reactants during a chemical reaction
B the total number of molecules before an after a chemical reaction stays the same
C Adams created during a chemical reaction must have the same mass as the atoms in the reactants
D Adams can be rearranged during a chemical reaction, but cannot be added or taken away

C Adams created during a chemical reaction must have the same mass as the atoms in the reactants