C
The African elephant , the largest land animal remaining on earth , is of great importance to African ecosystem（生态系统）. Unlike other animals , the African elephant is to a great extent the builder of its environment . As a big plant-eater , it largely shapes the forest-and-savanna（大草原） surroundings in which it lives , therefore setting the terms of existence for millions of other animals that live in its habitat（栖息地）.
It is the elephant’s great desire for food that makes it a disturber of the environment and an important builder of its habitat . In its continuous search for the 300 pounds of plants it must have every day , it kills small trees and underbushes , and pulls branches off big trees . This results in numerous open spaces in both deep tropical forests and in the woodlands that cover part of the African savannas . In these open spaces are numerous plants in various stages of growth that attract a variety of other plant-eaters .
Take the rain forests for example . In their natural state , the spreading branches overhead shut out sunlight and prevent the growth of plants on the forest floor . By pulling down trees and eating plants , elephants make open spaces , allowing new plants to grow on the forest floor . In such situations , the forests become suitable for large hoofed plant-eaters to move around and for small plant-eaters to get their food as well .
What worries scientists now is that the African elephant has become an endangered species . If the elephant disappears , scientists say , many other animals will also disappear from vast areas of forest and savanna , greatly chaning and worsening the whole ecosystem .
64. What is the passage mainly about ?
A. Disappearance of African elephants .
B. Forests and savannas as habitats for African elephants .
C. The effect of African elephants’ search for food .
D. The eating habit of African elephants .
65. What does the underlined phrase “ setting the terms ” most probably mean ?
A. Fixing the time .                B. Worsening the state .
C. Improving the quality .           D. Deciding the conditions .
66. What do we know about the open spaces in the passage ?
A. They result from the destruction of rain forests .
B. They provide food mainly for African elephants .
C. They are home to many endangered animals .
D. They are attractive to plant-eating animals of different kinds .
67. The passage is developed mainly by_______.
A. showing the effect and then explaining the causes
B. pointing out similarities and differences
C. describing the changes in space order
D. giving examples