Botany, the study of plants, occupies a special position in the history of human knowledge. For many thousands of years it was the one field of awareness about which humans had anything more than the vaguest (含糊的) of insight. It is impossible to know today just what our Stone Age ancestors knew about plants, but from what we can observe of pre-industrial societies that still exist, a detailed learning of plants and their properties must extremely ancient. This is logical. Plants are the basis of the food pyramid for all living things, even for other plants. They have always been enormously important to the welfare of peoples, not only for food, but also for clothing, weapons, tools, eyes, medicines, shelter, and a great many other purposes. Tribes living today in the jungles of the Amazon recognized accurately hundreds of plants and know many properties of each. To them, botany, as such, has no name and is probably not even recognized as a special branch of knowledge at all.
Unfortunately, the more industrialized we become the farther away we move from direct contact with plants, and the less distinct our knowledge of botany grows. Yet everyone comes unconsciously on an amazing amount of botanical knowledge, and few people will fail to recognize a rose, an apple, or an orchid. When our Neolithic ancestors, living in the Middle East about 10,000 years ago, discovered that certain grasses could be harvested and their seeds planted for richer productions the next season, the first great step in a new association of plants and humans was taken. Grains were discovered and from them flowed the wonder of agriculture; cultivated crops. From then on, humans would increasingly take their living from the controlled production of a few plants, rather than getting a little here and a little there from many varieties that grew wild and the built up knowledge of tens of thousands of years of experience and close relationship with plants in the wild would begin fade away.
51. Which of the following statements about early humans is expressed in the passage?
A. They probably had extensive knowledge of plants.    
B. They thought there was no need to cultivate crops.     
C. They did not enjoy the study of botany.      
D. They placed great importance on the ownership of property.
52. What does the comment “This is logical.” In the first paragraph mean?
A. There is no clear way to determine the extent of our ancestor’s knowledge of plants.           
B. It is not surprising that early humans had a detailed knowledge of plants.
C. It is reasonable to assume that our ancestors behaved very much like people in pre-industrial societies.       
D. Human knowledge of plants is well organized and very detailed.
53. According to the passage, why has general knowledge of botany begun to fade?
A. People no longer value plants as a useful resource.       
B. Botany is not recognized as a special branch of science.
C. Research is unable to keep up with the increasing numbers of plants.
D. Direct contact with a variety of plants has decreased.
54. In the second paragraph, what is the author’s purpose in mentioning “ a rose, an apple, or an orchid”?
A. To make the passage more poetic.
B. To give an example of plant that are attractive.
C. To give botanical examples that all readers will recognize.
D. To explain the variety of botanical life.
55. According to the passage, what was the first great step toward the practice of agriculture?
A. The invention of agricultural tools and machinery.       
B. The development of a system of names for plants.
C. The discovery of grasses that could be harvested and replanted.         
D. The changing diets of early humans.