Concept:Passive vocabulary refers to words that you understand when you hear or see them, but do not frequently use yourself.Explanation:Active vocabulary includes words you regularly use while speaking and writing.Passive vocabulary includes words you recognise when listening or reading, but you cannot easily recall or use them in your own speech or writing.Passive vocabulary is larger than active vocabulary because you understand more words than you actively use.Learners try to convert passive words into active words over time.Answer:A. words which we use when we listen to them and read them