【正确答案】Open class is one whose membership is in principle infinite or unlimited. When new ideas, inventions, or discoveries emerge, new members are continually and constantly being added to the lexicon. Nouns, verbs, adiectives and many adverbs are all open-class items.

【答案解析】[解析] 本题考查开放类词汇的定义，考生也应了解封闭类、语素、词缀、渊根、派生、曲折及构词法等重要概念。