Ключевые слова: 20s, academic, adult, african, american, assistance, bending, boy, casual, caucasian, classmate, classroom, communication, concentration, desk, education, exam, examination, female, five, girl, high, holding, indoor, knowledge, learning, looking, male, multiethnic, occupation, paper, people, school, schoolchildren, schoolwork, showing, sitting, standing, student, study, studying, teacher, teenager, test, university, woman, women, writing, young,