Final answer:
King Arthur's leadership skills are the characteristics most likely drawn from Theseus, as both heroes exhibited remarkable ability to guide and unite people in their respective legends.
Step-by-step explanation:
The characteristics of King Arthur that are most likely drawn from the legendary Greek hero Theseus are his leadership skills. Theseus was known for his ability to lead, particularly evident in his slaying of the Minotaur and his role in various other adventures. Similarly, Arthur is renowned for his leadership of the Knights of the Round Table and his ability to unite people. While being chosen as king (A) and being challenged by others (B) are significant parts of Arthur's legend, they are not characteristics uniquely linked to Theseus. Likewise, great strength (C) is a common trait in many heroes and not specifically indicative of a connection to Theseus.