We're being asked to identify which Law or Theory states that “In a chemical reaction, matter is neither created nor destroyed”.
Let's define each options first:
a. Law of Definite Proportions - all samples of a compound, no matter on their origin or preparation has the same ratio in terms of their elements.
“In a chemical reaction, matter is neither created nor destroyed” is called
a. the Law of Definite Proportions.
b. the Scientific Method.
c. the Law of Multiple Proportions.
d. Dalton’s Atomic Theory.
e. the Law of Conservation of Mass.