Task: Question Answering
Input (English): 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  
 (A) combustion. (B) fixed proportions. (C) conservation of mass. (D) conservation of energy.
Output (English): C