According to the law of definite proportions,
a) the mass ratio of the elements in a pure compound is always the same.
b) if two same elements react to form two different compounds, their mass ratio stays the
same for both compounds.
c) samples that have the same mass ratio are always the same substance
d) the mass of the products is definitely the same as the mass of the reactants
e) when two elements react they always form one definite compound