什么是变压器线圈的极性？有何意义？

驾驶机动车超车后立即开启右转向灯驶回原车道。

阅读理解。

     When pets get sick,you can usually take them to an animal doctor or an animal hospital.Sometimes

animals are so sick or hurt that you shouldn't move them.That's why Dr.Bird,a veterinarian,has a traveling

hospital.Dr.Bird drives his hospital,which is really a van,to the animals.

     Dr.Bird has run the hospital for over 10 years,and he has saved the lives of many pets.The van has an

operating table,medicines and everything else he needs to treat animals.Dr.Bird says that there will soon be many more traveling hospitals to help sick or injured animals.

1. The best name is ________.

A. Why People Get Sick

B. A Traveling Hospital

C. Dogs Make Good Pets

D. A Very Sick Animal

2. Dr.Bird has run the hospital for ________.

A. 12 years

B. 10 years

C. 8 years

D. 20 years

3. The story says that Dr. Bird's hospital has ________.

A. thick rugs

B. no lights

C. toys

D. medicines

4. Dr. Bird is ________.

A. a dentist

B. an animal doctor

C. very young

D. very sick

5. The word "veterinarian" means________.

A. animal doctor

B. nurse

C. farmer

D. truck driver

如图所示的系统中，弹簧的劲度系数为k = 39.2N/m，置于上面的物体质量m = 0.1kg，置于下面的物体质量M = 0.2kg。两物体之间的最大静摩擦力f_max = 0.196N。M与水平面之间是光滑的。若使两物体一起做简谐运动，要求

（1）画出该振动系统在平衡位置时下面物体的受力分析图

（2）该系统振动的最大振幅是多大

RADIUS协议中，CODE=1报文里可能携带的属性包括（）。

A.User-Name

B.FrameD.Protocol

C.FrameD.IP-Address

D.Filter-ID

《证券公司管理办法》规定，证券公司净资本不得低于其对外负债的( )。

A．4%

B．8%

C．10%

D．5%