题干

下列关于电流的说法中,正确的是    (    )

A:金属导体中,电流的传播速率就是自由电子定向移动的速率

B:温度升高时,金属导体中自由电子热运动加快,电流也就加大

C:电路接通后,电子就由电源出发,只要经过一个极短的时间就能达到用电器

D:通电的金属导体中,自由电子的运动是热运动和定向移动的合运动,电流的传播速率等于光速

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D

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    Speaking English is not only about using proper grammar.To use English effectively,you need to understand the culture in which it is spoken.Here are a number of important tips to remember when speaking English in the United States.

    Conversation tips.

    Talk about location____When speaking to strangers,ask them where they are from and then make a connection with that place.For example:“Oh,I have a friend who studied in Los Angeles.He says it's a beautiful place to live in.”  Most Americans will then willingly talk about their experiences living or visiting that particular city or area.

    Talk about work____It's not considered impolite and is a popular topic of discussion between strangers.

    Talk about sports.Americans love sports!____When speaking about football,most Americans understand “American Football”,not soccer.

    ____ Many Americans prefer first names.Americans often prefer using first names,even when dealing with people in very different positions.Americans will generally say,“Call me Tom.”and then expect you to remain on a first name basis.

    Public behavior.

    Always shake hands.____This is true for both men and women.Other forms of greeting such as kissing on the cheeks is generally not appreciated.

    Smoking is out!Smoking,even in public places,is strongly disapproved of by most Americans in the modem United States.

A.Addressing people.

B.Talking with people.

C.However,they love American sports.

D.Americans love to talk about location.

E.Americans commonly ask “What do you do?” .

F.Americans prefer to make friends with foreigners.

G.Americans shake hands when greeting each other.