(A) To make the passage more poetic

　　(B) To cite examples of plants that are attractive

　　(C) To give botanical examples that most readers will recognize

　　(D) To illustrate the diversity of botanical life

　　47. According to the passage, what was the first great step toward the practice  of agriculture ?

　　(A) The invention of agricultural implements 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

　　48. The word "controlled" in line 19 is closest in meaning to

　　(A) abundant

　　(B) managed

　　(C) required

　　(D) advanced

　　49. The relationship between botany and agriculture is similar to the relationship between zoology (the study of animals) and

　　(A) deer hunting

　　(B) bird watching

　　(C) sheep raising

　　(D) horseback riding

　　50. Where in the passage does the author describe the benefits people derive from plants?

　　(A) Line 1

　　(B) Lines 6-8

　　(C) Lines 10-11

　　(D) Lines 13-15