問題詳情

Questions 11-19The origins of nest-building remain obscure, but current observation of nest-buildingactivities provide evidence of their evolution. Clues to this evolutionary process can befound in the activities of play and in the behavior and movements of birds during mating,Line such as incessant pulling at strips of vegetation or scraping of the soil. During the early(5) days of the reproductive cycle, the birds seem only to play with the building materials. Inpreparation for mating, they engage in activities that resemble nest-building, and continuethese activities throughout and even after the mating cycle. Effective attempts at constructionoccur only after mating.Although nest-building is an instinctive ability, there is considerable adaptability in(10) both site selection and use of materials, especially with those species which build quiteelaborate constructions. Furthermore, some element of learning is often evident sinceyounger birds do not build as well as their practiced elders. Young ravens, for example,first attempt to build with sticks of quite unsuitable size, while a jackdaw's first nestincludes virtually any movable object. The novelist John Steinbeck recorded the contents(15) of a young osprey nest built in his garden, which included three shirts, a bath towel, andone arrow.Birds also display remarkable behavior in collecting building materials. Crows havebeen seen to tear off stout green twigs, and sparrowhawks will dive purposefully onto abranch until it snaps and then hang upside down to break it off. Golden eagles, over(20) generations of work, construct enormous nests. One of these, examined after it had beendislodged by high winds, weighed almost two tons and included foundation branchesalmost two meters long. The carrying capacity of the eagles, however, is only relative totheir size ant1 most birds are able to carry an extra load of just over twenty percent of theirbody weight.
11. The word "obscure" in line 1 is closest in meaning to
(A) interesting
(B) unclear
(C) imperfect
(D) complex

參考答案

答案：B
難度：適中0.5
統計：A(0),B(1),C(1),D(0),E(0)

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