A. Many Greek towns held sporting events with similar games.
Explanation:
When writing a paragraph, we mention the main idea along the first lines and then develop and support that idea in the following lines. In the paragraph we are analyzing here, the author's main idea is expressed in the very first sentence, "The Panathenaic Games was only one of several great religious sporting events held in Greece." From that point on, the author mentions the other several games that were held in Greece. He/She does include minor facts such as the cities where they were held, who could participate, and what sort of differences there could be between them. But the main reason for mentioning all those games is to provide evidence and support to the main idea that the Panathenaic was only of several sporting events.
D. Bilbo fears all Wargs because they are allies of the goblins. He is assuming that every Warg is out to get them because they are not aligned with the goblins and the Wargs are.