触电方式有（）触电、（）触电、（）触电。

旅游安全风险提示制度，主要指预先发现境内外旅游目的地对旅游者人身、财产可能造成损害的（）等潜在的或者已经存在的安全风险，提出旅游出行建议并按规定权限和程序，向社会公布。

A.自然灾害

B.社会安全事件

C.事故灾难

D.公共卫生事件

系统选样法的抽样间隔＝总体量÷（）×随机起数点。

A.抽样单位

B.金额单位

C.样本量

D.总体误差

阅读理解。

     In most towns today, you can see teenagers standing over electronic machines with flashing lights,

shooting at spaceships from other planets and dropping bombs on strange monsters (恶魔).The machines

have names like Space Warrior, Dark Invader and so on. It used to be believed that damage was done only

to those strange visitors from outer space, but now it seems that they are striking back.

     Many teenagers like electronic games so much that they can't stop playing.They spend hours tightly

holding the joystick controls and constantly pressing buttons marked"fire". They develop pains on their

fingers because of the constant pressure. They play and play so that the pains have no chance to cure

properly. The rapid wrist movement required to guide the spaceship across the screen causes another

problem: The muscles of the wrist and arm become so inflamed and swollen (红肿) that they press against

the bones. This condition is what doctors now call "Space Warrior's Wrist". Other strange aches and pains

also are likely to affect the elbows and shoulders.

     Another even more alarming problem is shown by the case of a 17-year-old girl which was recently in

the British Medical Journal. She had been playing various kinds of electronic games for more than two hours

a day. Her father repaired games and machines and she could use the cassettes and systems in his workshop

as often as she liked. One day, after playing a game called Dark Invader, she lost consciousness (晕倒) and

fell to the floor.

     Doctors who examined her found she was suffering from an unusual illness caused by lights flashing at

a particular frequency.

1. Electronic games are found very popular with __________.

A. people living in towns

B. students studying in high schools

C. girls working in their father's workshops

D. young people age about 15-20

2. "Space Warrior's Wrist" is caused by __________.

A. constantly pressing the buttons

B. rapidly moving across the screen

C. tightly holding the joystick controls

D. inflamed and swollen muscles of the wrist

3. The case of a 17-year-old girl by the writer shows that the writer __________.

A. supports playing electronic games

B. feels very sorry for the girl

C. disagreed with young people's playing electronic games

D. feels worried about young people's poor health

4. From the passage we can conclude that playing electronic games is __________.

A. enjoyable and helpful to the study

B. exciting but harmful to the health and study

C. interesting but harmless to the eyes

D. amusing and satisfying

下列污染物中，通过食物链危害人体的是 [ ]

A．沙尘暴

B．二氧化硫

C．汞、镉等有毒物质

D．氟利昂

双胎妊娠分娩时的处理，下列选项错误的是（）

A.第1胎儿娩出后立即断脐

B.如遇胎头交锁，可行断颈术

C.第1胎儿娩出后，立即固定另一胎儿为纵产式

D.第2胎儿胎肩娩出后，应立即注射催产素以防产后出血

E.第1胎儿娩出后，超过30min另一胎儿尚未娩出时，应行人工破膜