Final answer:
The quote is often attributed to a) Plato, but its exact source is not universally agreed upon.
Step-by-step explanation:
The quote 'No man has the right to be an amateur in the matter of physical training. It is a shame for a man to grow old without seeing the beauty and strength of which his body is capable.' is often attributed to Plato. However, it is important to note that the exact source of this quote is not universally agreed upon.
Plato was a Greek philosopher who emphasized the importance of both physical and intellectual education. He believed in the harmony between the body and the mind, and that physical training was essential for a well-rounded individual. However, it is worth mentioning that the exact wording of this quote cannot be attributed to Plato with certainty.