1952年12月英国伦敦地区发生一起严重的急性烟雾事件,导致数千人死亡这次伦敦烟雾事

题型:单项选择题

问题:

1952年12月英国伦敦地区发生一起严重的急性烟雾事件,导致数千人死亡

这次伦敦烟雾事件的主要污染物是

A.一氧化碳,二氧化碳

B.烟尘,二氧化硫

C.氮氧化物,臭氧

D.氟化物,金属颗粒

E.苯并(a)芘

考点:公卫执业助理医师公卫执业助理医师
题型:单项选择题

川崎病发生于5岁以下者()

A.1%~2%

B.<0.1%

C.15%~25%

D.50%

E.80%

题型:单项选择题

猎豹奔跑时所需要的能量直接来自于

A.太阳能

B.ATP

C.食物

D.呼吸作用

题型:单项选择题

社会变迁的内容

题型:单项选择题

下列说法正确的是

A.工业用SiO2与焦炭制取单质硅过程中,生成的气体产物是CO

B.硫在空气中燃烧的产物是SO­2­,在纯净氧气中燃烧的产物是SO3

C.钠在敞口容器中长期存放和在空气中燃烧的产物都是Na2O2

D.镁在空气中和纯净氧气中燃烧的产物都只有MgO

题型:单项选择题

In the 19th century, Americans from the eastern states moved out west to settle in the rich new lands along the Pacific Coast. The most difficult part of their trip was crossing “the Great American Desert” in the western part of the United States by horse and wagon.

The western desert can be very dangerous. There is little water and there are few trees. But the desert also has scenery of great beauty. Tall towers of red and yellow stone rise sharply from the flat, sandy valley floor. The scene has been photographed many times and appears in movies and on TV.

In Arizona, man-made dams across the Colorado River have made two large lakes in the middle of the dry desert country. At Lake Powell, the red stone arch of Rainbow Bridge rises high above the blue lake.

There are few roads. Many areas of Lake Powell’s shore can only be reached by boat or on foot. But hikers in this empty desert land sometimes find very old native American pictures, painted on the rocks.

In Death Valley, California, the summer temperature rises to 130°F—165°F. There is less than inches of rain each year. Death Valley is the lowest place in America---925 metres below sea level. In the 1800s, many travelers died when they tried to cross this waterless valley in the terrible heat.

Although the desert is dry and seems empty, there is plenty of life if you look closely. Snakes and rats have learned how to live in the desert heat. They live underground and come out at night, when it is cool. Plants such as cacti need very little water. When it does rain in the desert (sometimes only once or twice a year), plants grow quickly, and flowers open in a single day. For a short time, the desert is covered with brilliant (very bright) colours.

小题1:In the 19th century, Americans moved from east to west because they            .

A.enjoyed the trip

B.wanted to make their home there

C.wanted to find new grassland there

D.had no water to drink小题2:From this passage. we can conclude that         .

A.the western desert is a good place for people to live in

B.there is little water but there are many trees in the desert

C.the desert is dangerous but it is full of beauty

D.till now, people know little about the desert小题3:In the 1800s, many travelers died in Death Valley because of            .

A.illness

B.high temperature

C.cold weather

D.poisonous water小题4:In the desert, animals will die           .

A.if they move about

B.if they can’t make holes underground

C.if they come out at night

D.if they drink much water

更多题库