Ключевые слова: abc, agency, answer, ask, background, banner, blackboard, blank, blankness, board, chalk, chalkboard, classroom, concept, design, education, empty, faq, frame, frequently, graphic, help, icon, idea, information, interrogation, issue, knowledge, learning, letter, mark, matter, message, pattern, problem, question, question mark, sign, space, succor, support, symbol, teaching, text, title, topic, trouble, write,