Ключевые слова: ad, advertisement, advertising, advice, amazing, announcement, astonish, background, blackboard, blank, blankness, board, bulletin, chalk, chalkboard, circular, classroom, curious, disbelief, disbelieve, discredit, distrust, doubt, education, exclamation, exclamation mark, flat, glass, green, hesitation, impeach, incredulity, inquiring, inquiry, insignia, interrogation, interrogation mark, interrogative, issue, lacunae, mark, matter, misdoubt, misgiving, mishap, mistrust, notation, notice, notification, pattern, placard, plaint, plank, point, problem, proclamation, publicity, query, question, questioning, school, schoolroom, shock, sigh, sign, skepticism, suspect, suspicion, symbol, teaching, texture, topic, trouble, uncertainty, unknown factor, unsolved, wonder, wood, wooden, write,