In the 1700s, a French scientist, Antoine Lavoisier, gained new experimental information by reacting a metal and an acid. His observation of the results seemed to show that much of the metal had been lost in the chemical reaction. Upon weighing the products, the total amounts of materials had not changed during the reaction. This research resulted in the law of conservation of mass. This law also applies to biology, because the materials we are made of are that change forms, but aren't truly lost through biochemical reactions.

Matter

Explanation:

Matter refers to the atoms, molecules, compounds which we are composed of and our surrounding is made of.

The law of conservation of mass was proposed by the Antoine Lavoisier who stated that mass neither gained nor lost but changed its form from one form to another in his experiments.

The same law of conservation of mass applies to the biological organisms as like living things they are also made up of the matter. The metabolism of the chemical reaction taking place in the living organism is evidence of the law of conservation of mass.

Thus, the matter is correct.