Answer:
Theories develop through repeated experimentation.
Explanation:
The correct answer would be that theories develop through repeated experimentation.
A theory is internally consistent and is only arrived at after several independent experimentation based on the same phenomenon. That is, when a scientist reports a findings, the reports must have been widely tested by different researchers using the same experiment and arrive at similar findings before they can become a theory.
Hence, the information on the theory explaining the movement of sand beaches is valid because the experiment must have been repeated by several independent researchers and similar results must have been obtained before the theory is arrived at.