Back in the dining hall, Tris meets up with her friends. They discuss what jobs they might want if their ranking is high enough. Those with higher rankings get first pick—because if you're good at punching someone, you should be a good administrator.
And they're such good friends that they can discuss their fear landscapes: sex, moths (Christina's fear), etc.
The rankings are displayed then, and Tris is #1.
Even better, Molly and Drew don't do so well, so they get kicked out of the faction. Yay?
Tris kisses Tobias/Four in public, so, there goes the secret part of the relationship.
And that's when Tris realizes how Erudite will get Dauntless to fight for them, and it involves the serum. The answer is… just kidding, she doesn't tell us in this chapter.