请阅读 Passage 1 ,完成第21 ~ 25 小题。

                                                                       Passage 1

    The first two stages in the development of civilized man were probably the invention of primitive weapons and the discovery of fire, although nobody knows exactly when he acquired the use of the latter.The origin of language is also difficult Lo understand. No doubt it began very gradually. Animals have a few cries that serve as signals,but even the highest apes have not been found able to pronounce words,even with the most intensive professional instruction. The superior brain of man is apparently a necessity for the mastering of speech. When man became intelligent enough,we must suppose that he gradually increased the number of cries for different purposes. It was a great day when he discovered that speech could be used for describing and telling stones. There are those who think in this respect picture language appeared before oral language. A man could draw a picture on the wall of his cave to show in which direction he had gone,or what prey he hoped to catch. Probably picture language and oral language developed side by side.l prefer to think that language has been the most important single factor in the development of man.Two important stages came not so long before the dawn of written history. The first was the domestication of animals. The second was agriculture. Agriculture was a step Jn human progress to which there was nothing comparable until our own machine age. AgricuIture made possible an immense increase in the number of the human species in the regions where it could be successfully practi These were,at first,only those in which nature fenilized Llie soil after each hawest. Agricukure met  with violent resistance from the pastoral nomads,but the agriculturul way of life was accepted in the end because of the physical comlforts it provided.Another fundamental technical advance was writing,which,like spoken Ianguage,developed out of pictures,but as soon as it had reached a certain stage,it was possible to keep records and transmit Jnformation to people who were not present when the information was given.These inventions and discorreries-firc,speech,weapons,domestic animals,agriculture,and writing-made the exi8tence of civilized communitics possible. From about 3000 B. C. until the beginning of the Industrial Revolution less than two hundred years ago there was no technical advance comparable to these. During this long period man had time to become accustomed to his technique,and to develop the behefs and political organizations appropriate to it. There was,of course,an immense extcn-sion in the area of civilized life. AL first it had been confined to the Nile,the Euphrates,the 'rigris and the Indus,but at the end of the period in question it covered much the greater part of the inhabitalle globe.l do not mean to suggest that there was no technical progress during this Iong time-;there was progress-there were even two inventions of very great importance-,namely gunpowder and the compass-but neither of these can be comp8red in their power to such things as speech and writing and agriculture.