单选题 According to the passage, words are ______.
A. visual letters B. represented by sounds
C. represented either by sounds or letters D. signs called letters

【正确答案】 C

【答案解析】事实细节题。题目问“根据文章，单词是什么?”根据文章第一段最后一句“Those sounds，whether spoken，or written in letters we call words.”可以知道单词就是声音也可以代表字母，所以正确答案是C项。