Final answer:
Pi's mother distracts him with books when she can't answer his difficult questions, and Pi uses this opportunity to study Chinese works on astronomy.
Step-by-step explanation:
When Pi's mother is unable to answer his difficult questions, she tries to distract him with books. This is an example from the passage where Pi's father allows him to have books, leading to Pi's intensive study of Chinese works on astronomy. In the given text, Pi's mother is not directly mentioned reacting to his questions, but it can be inferred from the shared information that books serve as a means for Pi to engage in self-study and distraction when he cannot have discussions or find answers from his parents.