13．A new study has found that African elephants appear to use darkness to avoid being seen or heard when raiding（搜索） farmland for food．The study Also showed that elephants carry out their food raids based on the appearance of the moon，or lunar cycle．Researchers believe the animals are doing this during the cover of darkness to avoid contact with human beings．
A report on the study appeared in the African Journal of Ecology．Rachel Grant teaches animal behavior at Anglia Ruskin University in England．She says elephants are cathemeral，meaning they are active both day and night．But she says，their raids on crops almost always take place at night．This suggests that the animals go near villages when they sense that their huge bodies are more difficult to see
Ms．Grant added that an elephant's knowledge of the higher risk of being discovered on moonlit nights could explain its behavior during the lunar cycle．
The study was carried out in and around Mikumi National Park in Tanzania．The park has one of the largest populations of wild elephants in Africa．It is about 300kilometers west of Dar es Salaam．
The researchers chose five villages near the wildlife area and counted how many times elephants raided crops． They found that few of elephant"raid nights"took place during a full moon．The amount of crop damage．also fell considerably during such periods．
Rachel Grant says some elephants have what she calls"an internally arising biological rhythm（ 生物节律）"or they may be basing their decision-making on local conditions．In her words，"Many animals change their behavior according to varying light levels and the realizing risk of raiding foods．"She says this rhythm is likely to be a partly evolved，partly learned response．
Ms．Grant says the behavior probably is found in elephant populations in countries other than Tanzania．She adds that information from the study could be used to protect farms from elephant damage．
56．What is the text mainly about？A
A．A new finding about elephant behavior．
B．The relationship between animals and humans．
C．Wild elephants living in Tanzania．
D．A wildlife protection program in Africa．
57．African elephants mostly carry out their food raiding at nightC．
A．for fear of the sunlight B．to find more food
C．so as not to be discovered D．to avoid the hot weather
58．What does the underlined word"They"in Paragraph 5refer to？A
A．The researchers． B．The elephants． C．The crops． D．The villages
59．Ms．Grant believes that the biological rhythmsB．
A．only exist in elephants B．change with the living conditions
C．never change over time D．are all born with elephants
60．The finding of the study is helpful inD．
A．limiting the elephants'movements
B．increasing the elephants'population
C．changing the elephants'behavior
D．protecting the farmers'crops．
分析 本文是一篇科普类文章，主要讲述了一项新的研究发现，非洲大象通常在晚上出来寻找食物，研究者认为大象之所以晚上出来寻找食物是为了避免人类发现．本文以此展开谈论，讲述了研究者的调查过程及方式．
解答 56．答案：A．主旨大意题．根据"A new study has found that African elephants appear to use darkness to avoid being seen or heard when raiding（搜索） farmland for food"及全文内容可知，本文主要叫说了关于大象行为的新发现．故选A．
57．答案：C．细节理解题．根据"But she says，their raids on crops almost always take place at night．This suggests that the animals go near villages when they sense that their huge bodies are more difficult to see"可知，大象之所以这样做的原因是为了不被发现．故选C．
58．答案：A．推理判断题．根据此句前面一句"The researchers chose five villages near the wildlife area and counted how many times elephants raided crops"可推测出，they代指的是the researchers．故选A．
59．答案：B．细节理解题．根据"some elephants have what she calls"an internally arising biological rhythm（ 生物节律）"or they may be basing their decision-making on local conditions"可知，生物节律随环境的变化而改变．故选B．
60．答案：D．细节理解题．根据"She adds that information from the study could be used to protect farms from elephant damage"可知，这项发现可以用来保护农场免受大象的侵害．故选D．
点评 本文是一篇科普类阅读，题目涉及主旨大意题，细节理解题，推理判断题，做题时应结合文章上下文内容并根据所给选项的含义进行分析，从而得出正确答案．切记胡乱猜测，一定要做到有理有据．
