Final answer:
Jem reacts to Nathan Radley's actions with fear and curiosity, demonstrating his growing understanding of injustice and empathy towards others.
Step-by-step explanation:
In the novel 'To Kill a Mockingbird,' Jem reacts to Nathan Radley's actions with fear and curiosity. Jem has heard rumors about Nathan sealing the tree hole where Boo Radley leaves little gifts for Jem and Scout. When Jem discovers that the tree hole is indeed sealed, he becomes upset because he believes that Nathan is killing an innocent being and cutting off their connection to Boo Radley. Jem's reaction shows his growing understanding of injustice and his empathy towards others.