问题 选择题

下列说法正确的是(  )

A.白光和红光通过三棱镜都能发生光的色散现象

B.白光通过三棱镜形成彩色的光带,这个实验说明白光是复色光

C.不透明物体具有吸收光的能力,而透明物体则不能吸收光线

D.星星和月亮都能发光,都属于光源

答案

A、只有复色光,即白光能发生光的色散.故A不正确.

B、白光通过三棱镜形成彩色的光带,这个实验说明白光是复色光.故B正确.

C、透明体和不透明物体既具有吸收光的能力,也有反光的能力;故C不正确.

D、星星是光源,月亮不能发光,它是反射太阳光.故D不正确.

故选B

单项选择题
阅读理解

Few people would question the value of taking part in sports for young people.With proper training,supervision,protective equipment and techniques,and an proper emphasis on winning,sports can develop a healthy body and spirit and a life-long interest in being active and fit .Without such measures,childhood sports can lead to injuries and even paralysis or death.

Even in the best conditions,no activity can be risk—free.But most serious hazards are preventable.Cyclists and football players can reduce their risks by wearing helmets;hockey players by wearing masks;basketball and tennis players by wearing eye guards;baseball players by wearing batting helmets.

Besides,risks to individual players can often be found,and thus prevented,through a properly performed medical exam before a child plays.For accidents that may not be preventable,having an emergency plan and first-aid equipment,and someone trained to use the equipment,can be lifesaving.

Still,each year,according to the American College of Sports Medicine,more than 775,000 children under 14 are treated in emergency rooms for sports injuries,nearly half of them preventable.An estimated 300,000 athletes experience exercise—related head illnesses each year,and almost all of them should have been avoided.

Further,from half to three—fourths of sports-related concussions(脑震荡) are never even diagnosed;the injured are often sent back in to play too soon and put at risk of another more serious brain—damaging concussion.To help reduce these risks, the National Center for Sports Safety, with the National Athletic Trainers’ Association, offers a three-hour online safety course for coaches for $28 at www.SportsSafety.org.

1.Which of the following is true according to the passage?

A.All the accidents can be prevented.

B.All the accidents cannot be prevented.

C.Lives can be saved so long as there is proper equipment.

D.Lives cannot be saved even if there is proper equipment.

2.What does the underlined word “hazards”(in paragraph 2)mean?

A.mistakes          B.diseases           C.dangers            D.situations

3.It is implied in the passage that        .

A.prevention of injuries is not paid enough attention to

B.children under 14 are more easily hurt in sports

C.most head illnesses are related with exercise

D.none of the head illnesses should have happened

4.What can coaches mainly learn from the online safety course?

A.How to cure brain-damaging concussion.

B.How to diagnose brain-damaging concussion.

C.How to predict the possibility of brain damage.

D.How to deal with the injured properly.