Late at night, Ziling embarked on the last bus alone. There were only a few passengers on the bus, all of which were middle-aged men and women. Seeing that each of them was drowsy, Ziling chose a seat next to the window and sat down.Ziling is seventeen years old this year and is a senior high school student.But being a student does not mean that other students work hard every day to prepare for the college entrance examination.