Millie is a little girl who is at the age of nine. She is a pupil in a primary school. She works hard at her subjects. In class, she takes an active part in all kinds of activities. She looks smarter than her classmates. One day, she was doing her homework after supper as usual. Her father was not in. Her mother was taking a shower in the bathroom. After she finished her homework, Millie asked her mother to check it for her, but her mother didn't answer her. A few minutes later, her mother was still in the bathroom. Millie felt strange. She knocked at the door. But her mother had no answer. She pushed the door open and found her mother lying on the floor. At the same time, she smelled something terrible. It was the gas. She quickly opened the window, turned off the gas and called 120 and 110 for help. Soon some doctors and policemen came and sent her mother to the nearest hospital. Her mother was saved at last. Why did the little girl know how to do that? That was because she had learned how to save herself and others in danger in school. Although Millie is   _  , we should learn from her.
a primary school pupil a college student a nineteen-year-old girl a middle school student