Question

in any chemical reaction, the mass of the reactants equals the mass of the products. this result forms the basis of the law of conservation of mass. which statement can best verify why this is a law, rather than a theory?
it has both independent and dependent variables.
it has been tested with the latest laboratory balances, which are very accurate.
it describes a repeatedly observed relationship, but it does not offer an explanation.
it has more scientific evidence supporting it.

Explanation:

A law describes a repeatedly observed relationship (like the mass of reactants = mass of products in the Law of Conservation of Mass). A theory explains why (e.g., atomic - level processes). Since the Law of Conservation of Mass just states the mass relationship (observed fact) without explaining the "why" (like atomic interactions that cause it), this fits the definition of a law.

Answer:

It describes a repeatedly observed relationship, but it does not offer an explanation.