How old is Margie in the story?

Correct answer: Eleven years

The governing concept here is the accurate recall of a character detail from Isaac Asimov’s story. Margie is explicitly introduced as an eleven-year-old girl. Her age is important because it places her within the future system of home-based mechanical education and helps readers compare her with Tommy, who is thirteen. Therefore, option A is correct. Option B is a plausible distractor because thirteen is Tommy’s age, not Margie’s. Seven and fifteen are not ages assigned to either of these two children in the story. Remembering the pair—Margie eleven and Tommy thirteen—prevents confusion.