The Law of Definite Proportions agrees with Dalton's Atomic Theory so the answer is "c".

The law of definite proportions, also known as Proust's Law, states that a chemical compound contains the same proportion of elements by mass. This law is one of the foundations of stoichiometry and it arose from one of the assumptions of John Dalton's atomic theory dating back to 1803. This assumption was that when elements react, their atoms combine in simple, whole-number ratios. Therefore relative atomic weights could be figured from the percentage of elements in compounds. Dalton basically described the law of definite proportions by saying that compounds had specific atom to atom ratios.