利用SNIFFER进行攻击必须将网卡设置为哪种方式（）。A、广播方式 B、组播方式

以坐标轴为对称轴，以原点为顶点且过圆x²+y²-2x+6y+9=0的圆心的抛物线的方程是（　　）

A．y=3x²或y=-3x²

B．y=3x²

C．y²=-9x或y=3x²

D．y=-3x²或y²=9x

已知扇形的半径是12厘米，圆心角为30°，求：扇形的面积和周长．（保留π）

     Like distance runners on a measured course, all of us will move through time in a roughly predictable

pattern. In the first stage of our lives, we develop and grow, reaching toward the top of physical vitality.

After we grow up, however, the body begins a process of gradually wearing out.

     A new awareness of physical fitness may help lengthen our years of health and vitality, yet nothing we

do will work to stop the unavoidable force of aging.

Most of the changes of aging take place deep inside the body. The lungs become less able to take in

oxygen. Powerful muscles gradually lose their strength. The heart loses power and pumps less blood.

Bones grow easier to break.  

     Finally, we meet a stress, a stress that is greater than our physical resistance. Often, it is only a minor

accident or chance infection (a disease caused by virus), but this time, it brings life to an end.

In 1932, a classic experiment nearly doubled the lifetime of rats, simply by cutting back the calories in their diet. The reason for the effect was then unknown.

     Today, at the University of California at Berkley, Dr. Paul Seagle has also greatly lengthened the normal lifetime of rats. The result was achieved through a special protein limited diet, which had a great effect on

the chemistry of the brain. Seagle showed that within the brain, specific chemicals control many of the

signals that influence aging. By changing that chemical balance, the clock of aging can be reset.

    For the first time, the mystery of why we age is being seriously challenged. Scientists in many fields are

now making striking and far-reaching discoveries. An average lifetime lasts 75 years, yet in each of us lies

a potential for a longer life. If we could keep the vitality and resistance to disease that we have at age

twenty, we would live for 800 years.

1. What does the underlined word "it" refer to?

A. Physical vitality.    

B. Stress.

C. Aging.

D. Physical resistance.

2. Which of the following is not a change of aging？

A. The lungs become unable to take in oxygen.

B. People gradually lose their muscle strength.

C. The heart loses power and pumps less blood.

D. Bones tend to break more easily.

3. The author believes the following except that ________.

A. human's life pattern is predictable

B. physical fitness can't stop the force of aging

C. human's lifetime will last longer than 75 years

D. all of the changes of aging take place deep inside the body

4. How did Dr. Paul Seagle lengthen the lifetime of rats in his experiment?

A. By limiting the protein in their diet.

B. By cutting the calories in their diet.

C. By resetting their clock of aging.

D. By keeping their physical fitness.

5. What is probably the best title for the article?

A. Two Great Experiments  

B. The Mystery of Human Life

C. Ways to lengthen Human Life 

D. The Breakthrough in the Study of Aging

三叉神经痛和舌神经痛的首选药是（）

A.地西泮

B.阿司匹林

C.卡马西平

D.苯妥英钠

E.苯巴比妥

在平直轨道上甲、乙两物体相距为s，乙在前，甲在后，同时同向开始运动，甲以初速度V₁，加速度a₁，做匀加速运动．乙做初速度为零的匀加速运动，加速度为a₂，假定甲能从乙旁通过而互不影响，下列情况可能发生的是（）

A．当a1＝a2时，甲乙只能相遇一次

B．当a1>a2时，甲乙可能相遇两次

C．当a1>a2时，甲乙只能相遇一次

D．当a1<a2时，甲乙可能相遇两次