Answer:
Option C, Rocks break down over time
Explanation:
Since option D is incorrect as already stated the only option left is the optic C which can be considered as a theory. A theory is basically an explanation of a happening in the environment. For instance – Cameron is a rock which is found in the ocean floor (this is a fact and not a theory) thus any explanation which let us know how these rocks were formed , how they reached ocean bed , how they got deposited there etc, can be considered as a theory as it will explain the processes behind a fact.