Final answer:
Mrs. Murry knows that Meg and her brother are very smart because of their actions and high I.Q., which is a common way intelligence is recognized in literature.
Step-by-step explanation:
Mrs. Murry knows that Meg and her brother are very smart because of their demonstrated abilities and behaviors. For example, despite Peter not knowing machinery, he's considered wise for his age and has a high I.Q. Likewise, characters in similar contexts exhibit their intelligence through wit, academic pursuits, and artistic talents. In various texts, a character's intelligence is often perceived through their problem-solving skills, quick learning, interesting conversations, or even in the way they face challenges. These observations by parents, family members, and those who know them closely often contribute to the acknowledgment of their smart attributes.