Li Lu is a fifth-grade student who lived in a small village in Shanxi Province. She lived with her grandparents, because her parents are migrant workers in big cities. During the days when there were no school buses, Li Lu had to ride a bike five kilometers and climb a small mountain to school every day. Her 70-year-old grandfather says he and Li Lu's grandmother always worried about her safety. "There are so many cars on the roads, and we were really  _ about her all the time. When it was time for her to come home, we would stare at the alley's   entrance until she showed up." But with the start of the new school year, the school's new bus now picks up the students. Eleven-year-old Li Lu pointed at her seat on the bus and said ,"Now I don't ride my bike any more. My grandparents no longer need to worry about me. The bus is spacious and comfortable. Look! This is my seat, with my name tag on the seatback." What's the main idea of this passage?
Going to school by bike. Far away from school. Li Lu has taken the new school bus. Li Lu and her family.