Which detail best conveys Eric's growth through his development of empathy?

(5) Nils' directions were so explicit that a baby could have followed them, Eric felt.And here he was, nearing Red Oak, Iowa, and rocking backward and forward in despair. Never had he loved his brother so much, and never had the big world called to him so hard. But there was a lump in his throat which would not go down. Ever since nightfall he had been tormented by the thought of his mother, alone in that big house that had sent forth so many men.Her unkindness now seemed so little, and her loneliness so great. He remembered everything she had ever done for him: how frightened she had been when he tore his hand in the corn-sheller, and how she wouldn't let Olaf scold him. When Nils went away he didn't leave his mother all alone, or he would never have gone. Eric felt sure of that.

(6) The train whistled. The conductor came in, smiling not unkindly. "Well, young man, what are you going to do? We stop at Red Oak in three minutes."

(7) "Yes, thank you. I'll let you know."The conductor went out, and the boy doubled up with misery. He couldn't let his one chance go like this. He felt for his breast pocket and crackled Nils' letter to give him courage. He didn't want Nils to be ashamed of him. The train stopped.Suddenly he remembered his brother's kind, twinkling eyes, that always looked at you as if from far away. The lump in his throat softened. "Ah, but Nils, Nils would understand!" he thought. "That's just it about Nils; he always understands."