British cancer’ researchers have found that childhood leukaemia is caused by an infection and clusters of cases around industrial sites are the result of population mixing that increases exposure. The research published in the British Journal of Cancer backs up a 1988 theory that some as yet unidentified infection caused leukaemia--not the environmental factors widely blamed for the disease.
"Childhood leukaemia appears to be an unusual result of a common infection," said Sir Richard Doll, an internationally-known cancer expert who first linked tobacco with lung cancer in 1950. "A virus is the most likely explanation. You would get an increased risk of it if you Suddenly put a lot of people from large towns in a rural area, where you might have people who had not been exposed to the infection. " Doll was commenting on the new findings by researchers at Newcastle University, which focused on a cluster of leukaemia cases around the Sellafield nuclear reprocessing plant in Cumbria in northern England. Scientists have been trying to establish why there was more leukaemia in children around the Sellafield area, but have failed to establish a link with radiation or pollution. The Newcastle University research by Heather Dickinson and Louise Parker showed the cluster of cases could have been predicted because of the amount of population mixing going on in the area, as large numbers of construction workers and nuclear staff moved into a rural setting. "Our study shows that population mixing can account for the (Sellafield) leukaemia cluster and that all children, whether their parents are incomers or locals, are at a higher risk if they are born in an area of high population mixing," Dickinson said in a statement issued by the Cancer Research Campaign, which publishes the British Journal of Cancer.
Their paper adds crucial weight to the 1988 theory put forward by Leo Kinlen, a cancer epidemiologist at Oxford University, who said that exposure to a common unidentified infection through population mixing resulted in the disease.

A:Radiation has contributed to the disease B:Putting a lot of people from rural area in a large towns increases the risk of childhood leukaemia C:Population mixing is the most important reason for leukaemia cluster D:Childhood leukaemia is caused by an unusual infection

Telephone books in the United States have white, blue and yellow pages. The white pages list people with phones by last name, the blue pages contain numbers of city services, government agencies and public schools. Businesses and professional (专业的) services are listed in a special section, "the yellow pages. To make a long-distance call, you need an area code. Each area in the U. S. has an area code. The area covered by one area code may be small or large. For example, New York City has one area code, but so does the whole state of Oregon. If you want to know the area code of a place, you can look it up in the area code map, which is printed in the front of the white pages.
There are a lot of publlic telephones in the US. They have their own numbers. If you are making a long-distance call on a pubic telephone and run out of money, give the number on you phone to the person you are talking to, then hang up the receiver, and he can call you back. If you make a long-distance call and get a wrong number, call the operator and explain what happened. This means that you can make the call again to the right number without having to pay more money.

A:When you run out of money, you can ask your partner to call back. B:Telephone books in the US have different colors. C:The state of Oregon has several area codes. D:An area code is necessary in making a long-distance call.

Telephone books in the United States have white, blue and yellow pages. The white pages list people with phones by last name, the blue pages contain numbers of city services, government agencies and public schools. Businesses and professional (专业的) services are listed in a special section, the yellow pages. To make a long-distance call, you need an area code. Each area in the U. S. has an area code. The area covered by one area code may be small or large. For example, New York City has one area code, but so does the whole state of Oregon. If you want to know the area code of a place, you can look it up in the area code map, which is printed in the front of the white pages.
There are a lot of publlic telephones in the US. They have their own numbers. If you are making a long-distance call on a pubic telephone and run out of money, give the number on you phone to the person you are talking to, then hang up the receiver, and he can call you back. If you make a long-distance call and get a wrong number, call the operator and explain what happened. This means that you can make the call again to the right number without having to pay more money.
Which of the following statement is NOT true

A:When you run out of money, you can ask your partner to call back. B:Telephone books in the US have different colors. C:The state of Oregon has several area codes. D:An area code is necessary in making a long-distance call.

VBA中用实际参数a和b调用有参过程Area(m，n)的正确形式是 ______。

A:Area m,n B:Area a,b C:Call Area(m,n) D:Call Area a,b

VBA中用实际参数a和b调用有参数Area(m, n)的正确形式是( )。

A:Area m, n B:Area a, b C:Call Area (m, n) D:Call Area a, b

VBA中用实际参数a和b调用有参过程Area(m,n)的正确形式是 ______。

A:Area m,n B:Area a,b C:Call Area(m, D:Call Area a,b

VBA中用实际参数a和b调用有参数Area(m, n)的正确形式是( )。

A:Area m, n B:Area a, b C:Call Area (m, D:Call Area a, b

"If an area to be avoided is a circle, the largest diameter is likely to be ______．

A:hundreds of miles B:less than one hundred of miles C:several miles D:one mile"