题目

How men first learned to invent words is unknown; in other words, the origin of language is a mystery. All we really know is that men, unlike animals, somehow invented certain sounds to express thoughts and feelings, actions and things, so that they could communicate with each other; and that later they agreed upon certain signs, called letters, which could be combined to represent those sounds, and which could be written down. Those sounds, whether spoken, or written in letters we call words. The power of words, then, lies in their combinations - the things they bring up before our minds. Wor(2018承德二模)You should________ what you have learned in time. It's necessary for your study.A.standB.createC.replyD.review