平行四边形ABCD中，对角线AC、BD相交于点O，若E、F是线段AC上的两动点，

Children attending schools located in high-traffic zones have a 45 percent increased risk of developing asthma, even though time spent at school only accounts for about one-third of a child’s waking hours, according to new research.

Asthma is the most common chronic childhood illness in developed countries and has been linked to environmental factors such as traffic-related air pollution. "While residential traffic-related pollution has been associated with asthma, there has been little study of the effects of traffic exposure at school on new onset asthma," says Rob McConnell, professor of preventive medicine at USC’s Keck School of Medicine. "Exposure to pollution at locations other than home, especially where children spend a large portion of their day and may engage in physical activity, appears to influence asthma risk as well."

The study appears online in the journal Environmental Health Perspectives. The study drew upon data from the Children’s Health Study (CHS), a longitudinal study of children in Southern California communities that was designed to investigate the chronic effects of air pollution on respiratory health. Using a cohort of 2 497 kindergarten and first grade children who were asthma-free when they entered the study, researchers examined the relationship of local traffic around schools and homes to diagnosis new onset asthma that occurred during three years of follow-up. Traffic-related pollution exposure was assessed based on a model that took into account traffic volume, distance to major roadways from home and school and local weather conditions.

Regional ambient ozone, nitrogen dioxide (二氧化氮) and particulate matter were measured continuously at one central site in each of the 13 study communities. The design allowed investigators to examine the joint effects of local traffic-related pollution exposure at school and at home and of regional pollution exposure affecting the entire community. Researchers found 120 cases of new asthma. The risk associated with traffic-related pollution exposure at schools was almost as high as for residential exposure, and combined exposure accounting for time spent at home and at school had a slightly larger effect. Although children spend less time at school than at home, physical education, and other activities that take place at school may increase ventilation rates and the dose of pollutants getting into the lungs, McConnell notes. Traffic-related pollutant levels may also be higher during the morning hours when children are arriving at school.

Despite a state law that prohibits school districts from building campuses within 500 feet of a freeway, many Southern California schools are located near high-traffic areas, including busy surface streets.

"It’s important to understand how these micro-environments where children spent a lot of their time outside of the home are impacting their health," McConnell says. "Policies that reduce exposure to high-traffic environments may help to prevent this disease. " The study was funded by grants from the National Institute of Environmental Health Sciences, the US Environmental Protection Agency, the South Coast Air Quality Management District, and the Hastings Foundation.

Which of the following is TRUE according to the text（）

A.In Southern California, many schools are located near heavy traffic zones

B.The study was carried out by many organizations

C. Rob McConnell is the leader of the study

D. Asthma is the most common chronic childhood illness around the world

小细胞不均一性贫血时（）

A.MCV减少，RDW正常

B.MCV减少，RDW增高

C.MCV及RDW均正常

D.MCV正常，RDW增高

E.MCV增高，RDW正常

画出图中力F的力臂。

进口报关单上的进口日期应填报实际货物进境的日期。( )