A Chemist Measures the Masses of Two Substances Separately, Then

A chemist measures the masses of two substances separately, then combines them in a reaction flask and heats the mixture.After several minutes, the chemist cools the flask and measures the mass of the contents.The final mass of the contents is less than the sum of the masses of the two substances placed in the flask before heating.Which statement provides a possible explanation for this observation?

A) Physical changes in the two starting substances resulted in products with less combined mass than the starting substances.
B) Heating caused the substances to melt, which resulted in a change in overall volume and mass.
C) The two starting substances absorbed energy from the heat, which destroyed some of the atoms making up the substances.
D) Only one product was formed from the combination of two reactants, resulting in less overall mass at the end.
E) The two starting substances underwent chemical change to produce two products, one of which was a gas.