After the passage of a cold front the visibility ______.A.does not changeB.improves rapidlyC.improves only slightlyD.becomes poor

What should you do if you have to work in front of the computer?

On a working copy of a weather map，a cold front is represented by what color line? （）

A cold front moving in from the northwest can produce（）.

请阅读 Passage 2，完成第 26~30小题。Passage 2 The common cold is the world's most widespread illness， which is plague that flesh receives.The most widespread fallacy of all is that colds caused by cold.They are not， They are caused by viruses passing on from person to person.You catch a cold by coming into contact， directly or indirectly， with someone who already has one.If cold causes colds， it would be reasonable to expect the Eskimos to suffer from them forever.But they do not.And in isolated arctic regions explorers have reported being free from colds until coming into contact again with infected people from the outside world by way of packages and mail dropped from airplanes.During the First World War soldiers who spent long periods in the trenches， cold and wet，showed no increased tendency to catch colds.In the Second World War prisoners at the notorious Auschwitz concentration camp， naked and starving， were astonished to find that they seldom had colds.At the Common Cold Research Unit in England， volunteers took part in Experiments in which they gave themselves to the discomforts of being cold and wet for long stretches of time.After taking hot baths， they put on bathing suits， allowed themselves to be with cold water， and then stood about dripping wet in drafty room.Some wore wet socks all day while others exercised in the rain until close to exhaustion.Not one of the volunteers came down with a cold unless a cold virus was actually dropped in his nose.If， then， cold and wet have nothing to do with catching colds， why are they more frequent in the winter? Despite the most pains-taking research， no one has yet found the answer， One explanation offered by scientists is that people tend to stay together indoors more in cold weather than at other times， and this makes it easier for cold viruses to be passed on.No one has yet found a cure for the cold.There are drugs and pain suppressors such as aspirin， but all they do is relieve the symptoms.Which of the following does not agree with the passage?

请阅读 Passage 2，完成第 26~30小题。Passage 2 The common cold is the world's most widespread illness， which is plague that flesh receives.The most widespread fallacy of all is that colds caused by cold.They are not， They are caused by viruses passing on from person to person.You catch a cold by coming into contact， directly or indirectly， with someone who already has one.If cold causes colds， it would be reasonable to expect the Eskimos to suffer from them forever.But they do not.And in isolated arctic regions explorers have reported being free from colds until coming into contact again with infected people from the outside world by way of packages and mail dropped from airplanes.During the First World War soldiers who spent long periods in the trenches， cold and wet，showed no increased tendency to catch colds.In the Second World War prisoners at the notorious Auschwitz concentration camp， naked and starving， were astonished to find that they seldom had colds.At the Common Cold Research Unit in England， volunteers took part in Experiments in which they gave themselves to the discomforts of being cold and wet for long stretches of time.After taking hot baths， they put on bathing suits， allowed themselves to be with cold water， and then stood about dripping wet in drafty room.Some wore wet socks all day while others exercised in the rain until close to exhaustion.Not one of the volunteers came down with a cold unless a cold virus was actually dropped in his nose.If， then， cold and wet have nothing to do with catching colds， why are they more frequent in the winter? Despite the most pains-taking research， no one has yet found the answer， One explanation offered by scientists is that people tend to stay together indoors more in cold weather than at other times， and this makes it easier for cold viruses to be passed on.No one has yet found a cure for the cold.There are drugs and pain suppressors such as aspirin， but all they do is relieve the symptoms.The passage mainly discusses ____.

Which of the following statements concerning frontal movements is TRUE（）.

After the passage of a cold front the visibility（）.

According to the information given in the passage, sulfur dioxide emissions are linked to all except which of the following phenomena?

Jim was absent from school for the whole week ______ a bad cold.

Cyclones tend to move（）.

The height of a tide can be increased by（）.

Cyclones that have warm sectors usually move（）.

After walking hurriedly for half an hour, I wanted to drink （）

After a cold front passes the barometric pressure usually（）.

After a cold front passes，the barometric pressure（）.