Final answer:
Deza's father goes missing on the last day of school, which is a devastating event for him.
Step-by-step explanation:
In the book referenced, Deza is the main character who experiences a devastating event on the last day of school. The answer is (b) His father goes missing. Deza's father disappears, leaving him feeling sad and abandoned. This event sets the stage for the protagonist's determination to use his intelligence to overcome challenges and make his mark in the world.