Which logical fallacy is used in the text?
How do I know that Meg is the most intelligent person in our geometry class? I know because she's so smart.

 - ad hominem: a personal attack against one's opponent
 - circular reasoning: an argument that supports a claim with the claim itself
The text argues that Meg is intelligent because she's smart. However, the "evidence" is just a restatement of the claim itself. This illustrates a type of logical fallacy known as circular reasoning.