Final answer:
The saying 'An apple a day keeps the doctor away' is a hypothesis, which is an untested statement suggesting that healthy eating promotes better health, and is not a scientific fact, law, or confirmed theory.
Step-by-step explanation:
A hypothesis is a tentative explanation for an observation, while a scientific theory is a well-substantiated and confirmed explanation for a set of observations or phenomena. A scientific law, on the other hand, is a description of the behavior of an aspect of nature. The statement "An apple a day keeps the doctor away" is best described as a hypothesis. It is a saying that suggests the idea that eating healthy food can lead to better health, which could in turn reduce the need to visit a doctor. However, as it stands, this statement is not a scientifically proven fact, a descriptive law, or a theory that has been repeatedly tested and confirmed.