Ключевые слова: 20, abstract, background, blue, care, celebration, concept, day, earth, eco, ecology, energy, environment, environmental, flat, global, globe, green, happiness, holiday, isolated, lay, letter, life, light, line, march, natural, nature, number, outline, paper, person, planet, protection, round, science, shape, sheet, solar, space, spring, summer, symbol, top, twenty, view, white, word, world,