Question

in the late 1700s, antoine lavoisier performed a series of experiments to find out what happened when a substance burned. in each experiment, he observed that the weight of a container and its contents was the same at the end of the experiment as it had been in the beginning. these observations led him to propose the law of
conservation of energy
conservation of mass
fixed proportions
combustion.

Explanation:

Lavoisier's experiments showed that the total mass of a closed - system (container and its contents) remained constant before and after a substance burned. This led to the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction.

Answer:

B. conservation of mass