[单项选择] How men first learned to invent words is unknown; (31)____, the origin of language is a mystery. All we really know is that men, unlike animals, somehow invented certain (32)____ to express thoughts and feelings, actions and things, (33)____ they could communicate with each other; and that later they agreed (34)____ certain signs, called letters, which could be (35)____ to represent those sounds, and which could be (36)_____. Those sounds, whether spoken, (37)_____ written in letters, we call words. The power of words, then, lies in their (38)____ the things they bring up before our minds. Words become (39)____ with meaning for us by experience; (40)._____ the longer we live, the more certain words (41)_____ to us the happy and sad events of our past: and the more we (42)____, the more the number of words that mean something to us (43)____ Great writers are those who not only have great thoughts but also express these thoughts in words which appeal (44)____ to our minds a
A. written down
B. handed down
C. remembered
D. observed