Human beings have used tools for a very long time. In some parts of the world you can still find tools that people used more than two million years ago. They made these tools by hitting one stone against another. In this way, they broke off pieces from one of the stones. These chips of stone were usually sharp on one side. People used them for cutting meat and skin from dead animals, and also for making other tools out of wood.  

Human beings needed to use tools because they did not have sharp teeth like other meat eating animals, such as lions and tigers. Tools helped people to get food more easily. Working with tools also helped to develop human intelligence. The human brain grew bigger, and human beings began to invent more and more tools and machines. The stone chip was one of the first tools that people used, and perhaps it is the most important. Some scientists say that it was the key to success of mankind.?  

24. The stone chip is thought to be the most important tool because it ______.
A. was one of the first tools?  

B. developed human capabilities?  

C. led to the invention of machines?  

D. was crucial to the development of mankind ?  

25. At the end of the passage the author seems to suggest that life in future is ______.?  

A. disastrous B. unpredictable C. exciting D. colorful  

答案解析： 

24. D) 这是一道细节题。根据文章第二段尾句“Some scientists say that it was the key to the success of mankind”可知“stone chip”对于人类的发展起到了非常重要的作用，这与D正好相符。    

25. B) 在文章最后一段中作者说人类在过去的几百万年时间里一直使用“stone chip”，人类社会发生的变化很小。而我们使用“silicon chips”才不过几年，生活却发生了巨大的变化。于是作者发出了疑问：“二十年后的生活会是什么样子的呢？”，“ 二百万年后的世界又会是什么样子呢？”，表明将来的生活无法预料，这与选项B相符。