Ключевые слова: addiction, black, blackboard, blackboards, board, cancer, chalk, chalkboard, chemical, chemistry, cigarette, class, classroom, college, concept, drawing, drugs, education, element, formula, green, hand, health, learning, lung, medical, medicine, model, molecular, molecule, molecules, nicotine, school, science, sign, smoke, smoking, stop, structural, structure, student, symbol, teacher, teaching, text, texture, tobacco, university, white, writing,