When it es to social behaviour，mammals are in a league of their own.Some birds may form pairs，or even cooperate to hunt，but the plexity (复杂性) of their relationships can hardly pare to those within a school of dolphins，a herd of elephants or a group of humans.What makes mammalian social groups different from a flock of starlings or a shoal of fish，is that in many cases the individuals could recognize each other.Although we may think that all elephants look pretty much the same，we can easily tell individuals of our own species apart and it has bee clear through studies that the same is true of other species.Dolphins have their own signature whistles that act like “names”，and elephants can recognize and greet other individuals they have known but not seen for many years.This is something that only a few species of birds appear to be able to do.
Mammals in plex social groups not only recognize each other as individuals，but also they remember a lot of information about that individual.Social groups often rely on this memory—such as knowing who is dominant to whom，who is related to whom，and who has done what to whom in the past.It’s like remembering who you have lent money to or done a favour for，and who hasn’t repaid that money or has talked about you behind your back.You have to learn who to trust，who your friends are，and who to watch out for.
All this remembering goes on in a particular part of the brain called the neocortex (大脑皮层)．If you pare the size of a mammal’s social group with the size of this part of the brain，you will find they are remarkably closely related.This area seems to take a long time to develop fully and animals in which it is very large take a very long time to grow up to adulthood.During this time，the youngster has to learn all the rules of social behaviour in their group and to piece together all the relationships between the group members：Knowledge that will be needed to avoid getting into trouble.
【小题1】What is special about a mammalian social group according to the passage?A．All the individuals cooperate to hunt.B．The individuals can municate with each other.C．The individuals can recognize each other.D．The individuals form closer relationship.【小题2】The passage suggests that elephants .A．are cleverer than dolphinsB．can recognize other speciesC．may mistake a member for anotherD．have good memories【小题3】Animals whose area of the neocortex is large .A．will have a long period of time before they bee adultsB．will spend a shorter time learning the necessary knowledgeC．will learn the necessary knowledge much more easilyD．will have more difficulty in growing up as adults【小题4】If the neocortex is larger，the animals .A．can live a longer lifeB．have a smaller social groupC．have a larger social groupD．have a greater body sizeC
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(答案→)C
解析：
【小题1】 C
解析 细节理解题。由文章第一段第三句可知，哺乳动物的一大特点是，一个群体中的每个个体都能辨认出其他的个体。
【小题2】 D
解析 推理判断题。文章第一段倒数第二句说明，大象如果彼此认识，即使它们多年不见，但重新见面后也能认出对方互相打招呼，这说明它们记忆力很好。
【小题3】 A
解析 细节理解题。由文章最后一段第三句可知，如果一个动物的大脑皮层很大，那么它成年所需的时间也就更长。
【小题4】 C
解析 推理判断题。由文章最后一段可知，动物大脑皮层部位的大小与它群体的大小存在正相关的关系。故大脑皮层大，对应的社会群体也大。