how does katniss show selflessness?

Page numbers are different in the many publications of this book. I can include the chapter. Here Katniss volunteers herself in the place of her little sister for the games.

Prim!" The strangled cry comes out of my throat, and my muscles begin to move again. "Prim!" I don't need to shove through the crowd. The other kids make way immediately allowing me a straight path to the stage. I reach her just as she is about to mount the steps. With one sweep of my arm, I push her behind me.

"I volunteer!" I gasp. "I volunteer as tribute!" ch 2