单选题 Stanford University scientists have weighed in on the "maybe not" side of the debate after an extensive examination of four decades of research comparing organic and conventional foods. They concluded that fruits and vegetables labeled organic were, on average, not more nutritious than their conventional counterparts, which tend to be far less expensive. Nor were they any less likely to be contaminated by dangerous bacteria like E. coli. The researchers also found no obvious health advantages of organic meats.
Conventional fruits and vegetables did have more pesticide residue, but the levels were almost always under the allowed safety limits, the scientists said. "When we began this project, we thought that there would likely be some findings that would support the superiority of organics over conventional foods," said Dr. Dena Bravata, a senior affiliate of Stanford"s Center for Health Policy and the senior author of the paper, which appears in Tuesday"s issue of the Annals of Internal Medicine. "I think we were definitely surprised."
In the study—known as a meta-analysis, in which previous findings are aggregated but no new laboratory work is conducted—researchers combined data from 237 studies, examining a wide variety of fruits, vegetables and meats. For four years, they performed statistical analyses looking for signs of health benefits from adding organic foods to the diet.
The researchers did not use any outside financing for their research. "I really wanted us to have no perception of bias," Dr. Bravata said.
The study"s conclusions about pesticides did seem likely to please organic food customers. Over all, the Stanford researchers concluded that 38 percent of conventional products tested in the studies contained detectable residues, compared with 7 percent for the organic produce. (Even products grown organically can be tainted by pesticides wafting over from a neighboring field or during processing and transporting.) They also noted a couple of studies that showed that children who ate organic produce had fewer pesticide traces in their urine.
Dr. Bravata agreed that people bought organic food for a variety of reasons—concerns about the effects of pesticides on young children, the environmental impact of large-scale conventional farming and the potential public health threat if antibiotic-resistant bacterial genes jumped to human pathogens. "Those are perfectly valid," she said.
But if the choices were based mainly on the hope that organic foods would provide more nutrients, "I would say there is no robust evidence to choose one or the other," Dr. Bravata said.

单选题 According to Dr. Bravata, it is ______ for people to think that organics are better than conventional foods.

单选题 Which of the following statements is TRUE?

单选题 People bought organic foods for different reasons EXCEPT ______.

单选题 What does the last sentence mean?

单选题 The passage focuses on ______.