The fragment <em>near the computer </em>is a prepositional phrase. Since it begins with a preposition <em>near </em>and it doesn't have a verb, it must be a prepositional phrase.
The correct answer is satire.
Twain is being very satirical when he wrote about Jim and Huck talking about King Solomon. According to the Bible, King Solomon was the wisest man of them all, but Huck doesn't understand how that could be possible due to what he learned about such people during his life. So Twain tried to mock formal education and religion through this discussion.