4. According to the Wynne-Edwards theory as it is described in the passage, epideictic behavior displays serve the function of

　　(A) determining roosting aggregations

　　(B) locating food

　　(C) attracting predators

　　(D) regulating sexual activity

　　(E) triggering hormonal changes

　　5. The challenge posed to the Wynne-Edwards-theory by several studies is regarded by the author with

　　(A) complete indifference

　　(B) qualified acceptance

　　(C) skeptical amusement

　　(D) perplexed astonishment

　　(E) agitated dismay

　　6. Which of the following statements would provide the most of logical continuation of the final paragraph of the passage?

　　(A) Thus wynne-Edwards' theory raises serious questions about the constancy of animal population in a region.

　　(B) Because Wynne-Edwards' theory is able to explain more kinds of animal behavior than is the density- dependent theory, epideictic explanations of population regulation are now widely accepted.

　　(C) The results of one study, for instance, have suggested that group vocalizing is more often used to defend territory than to provide information about population density.

　　(D) Some of these studies have, in fact, worked out a systematic and complex code of social behavior that can regulate population size.

　　(E) One study, for example, has demonstrated that birds are more likely to use winter-roosting aggregations than group vocalizing in order to provide information on population size.