Read the passage and choose the correct answer

　　One of the animals that helps people most is the dog. In some countries, dogs pull wagons(四轮马车)like horses. In the cold land of the North, dogs pull sledges(雪橇).

　　There are other ways that dogs help us, too. Policemen use them to look for missing people. Soldiers(士兵)use them to carry letters and medicines.

　　On farms, dogs are used to watch sheep. They keep them together in the fields. At night, they take the sheep home. Dogs help blind people(盲人), too.

　　Different dogs do different kinds of work. Some are good at one kind, some are good at another. Do you know what kind of dogs takes care of sheep?

(1)In the North, dogs are used to pull ________.

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(2)Which of the following is true? ________

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A．All dogs can help to do any kind of work.

B．Dogs help blind people.

C．The kind of dogs that can pull sledges can also look after sheep.

D．Dogs help farmers by keeping the sheep together at home.

(3)The story as a whole is about ________.

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A．finding missing people

B．horses

C．pulling sledges

D．how dogs help people