The term sinewy most closely mean "athletic"
Option - A
Explanation:
Sinewy (relative increasingly strong, superlative generally strong) Tough; having solid ligaments. (Metaphorically) Having or indicating anxious quality. (Of an individual) possessing physical quality and weight; tough and amazing. It technically means that the person that’s being described is muscular but not lean or fat.
Therefore the question describer the old man, Joseph the elderly man as a strong muscular man who was old but muscular enough to be described as sinewy .