The power of words, then lies in their association with the things they bring up before our minds. Words became filled with meanings for us by experience; and the longer we live, the more certain words recall to us the glad and sad events of our past; and the more we read and learn, the more the number of words that mean something to us increase.
Great writers are those who not only have great thoughts but also express these thoughts in words that appeal powerfully to our minds and emotions. We should therefore learn to choose our words carefully and use them exactly, or they will make our speech silly and impolite.
The origin of language is ______.

A. clearly explained in this passage
B. a matter that can not be or has not been explained or understood
C. a question that was difficult to answer
D. a problem already solved