Dolphins（海豚）are not fish, but warm-blooded animals. They live in groups, and speak to each other in their own language. In this, they are like other animals, such as bees and birds. But dolphins are very different from almost all land animals. Their brain is nearly the same size as our own, and they live a long time―at least twenty or thirty years. Like some animals, dolphins use sound to help them find their way around. They also make these sounds to talk to each other and to help them find food. We now know they do not use their ears to receive these sounds, but the lower part of the mouth, called the jaw.
Strangely, dolphins seem to like man, and for thousands of years there have been stories about the dolphin and its friendship with people.
There is a story about sailors in the 19th century. In a dangerous part of the sea off the coast of New Zealand, they learnt to look for a dolphin called Jack. From 1871 to 1903, Jack met every boat in the area and showed it the way. Then in 1903 a passenger on a boat called The Penguin shot and wounded Jack. He recovered and for nine years more continued to guide all ships through the area－except for The Penguin.
Today, some people continue to kill dolphins, but many countries of the world now protect them and in these places it is against the law to kill them.
【小题1】Dolphins are different from many other animals in that they _____.

Reading Comprehension

Read the following passages, and choose the best answer that can answer the question.

　　Dolphins are not fish, but warm－blooded animals. "I hey live in groups, and speak to each other in their own language. In this they arc like other animals, such as bees and birds. But dolphins are very different from almost all land animals. Their brain is nearly the same size as our own, and they live a long time－at least twenty or thirty years.

　　Like some animals, dolphins use sound to help them find their way around. They also make these sounds to talk to each other and to help them find food. We now know they do not use their ears to receive these sounds, but the lower part of the mouth, called the jaw.

　　Strangely, dolphins seem to like man, and for thousands of years there have been stories about the dolphin and its friendship with people.

　　There is a story about sailors in the 19th century. In a dangerous part of the sea off the coast of New Zealand, they learnt to look for a dolphin called Jack. From 1871 to 1903 Jack met every boat in the area and showed it the way. Then in 1903 a passenger on a boat called the Penguin shot and wounded Jack. He recovered and for nine years more continued to guide all ships through the area－except for the Penguin.

　　Today, some people continue to kill dolphins, but many countries of the world now protect them and in these places it is against the law to kill them.

1．Dolphins are different from many other animals in that they ________.

[　　]

A．live in groups

B．have large brains

C．are warm－blooded

D．have their own language

2．Which of the following does the dolphin use to help it find its way around?

[　　]

3．Why did the sailors off the coast of New Zealand look for Jack?

[　　]

A．He was lonely and liked to be with people.

B．They enjoyed playing with him.

C．He was seriously wounded.

D．They wanted his help.

4．By telling the story of Jack the writer wanted to show that ________.

[　　]

A．dolphins are friendly and clever

B．people are cruel to animals

C．Jack is different from other dolphins

D．Dolphins should be protected by law

5．What does the underlined sentence tell use?

[　　]

A．Penguins used to guide the ships passing by.

B．There used to be penguins on the boat.

C．Jack guided for all ships except the boat called the Penguin.

D．Jack recovered with the help of the penguin.

When it comes to social behaviour，mammals are in a league of their own.Some birds may form pairs，or even cooperate to hunt，but the complexity (复杂性) of their relationships can hardly compare 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 become 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 complex 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 compare 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.

1.What is special about a mammalian social group according to the passage?

A．All the individuals cooperate to hunt.

B．The individuals can communicate with each other.

C．The individuals can recognize each other.

D．The individuals form closer relationship.

2.The passage suggests that elephants________.

A．are cleverer than dolphins

B．can recognize other species

C．may mistake a member for another

D．have good memories

3. Animals whose area of the neocortex is large________.

A．will have a long period of time before they become adults

B．will spend a shorter time learning the necessary knowledge

C．will learn the necessary knowledge much more easily

D．will have more difficulty in growing up as adults

4. If the neocortex is larger，the animals________.

A．can live a longer life

B．have a smaller social group

C．have a larger social group

D．have a greater body size