根据以下材料，回答36-40题
Although ethics classes are common around the world, scientists are unsure if their lessons can actually change behavior，evidence either way is weak，relying on contrived laboratory tests or sometimes unreliable self-reports. But a new study published in Cognition found that ,in at least one real-world situation, a single ethics lesson may have had lasting effects.
The researchers investigated one class session's impact on eating meat. They chose this particular behavior for three reasons, according to study co-author Eric Schwitgebel, a philosopher at the University of Califomnia, Riverside: student's attitudes on the topic are variable and unstable, behavior is easily measurable, and ethics literature largely agrees that eating less meat is good because it reduces environmental harm and animal suffering. Half of the students in four large philosophy classes read an article on the ethics of factory-farmed meat, optionally watched an 11-minute video on the topic and joined a 50-minute discussion. The other half focused on charitable giving instead. Then, unknown to the students, the researchers studied their anonymized meal-card purchases for that semester —nearly 14.000 receipts for almost 500 students.
Schwitzgebel predicted the intervention would have no effect; he had previously found that ethics professors do not differ from other professors on a range of behaviors，including voting rates, blood donation and returning library books. But among student subjects who discussed meat ethics, meal purchases containing meat decreased from 52 to 45 percent — and this effect held steady for the study's duration of several weeks. Purchases from the other group remained at 52 percent.
"That's actually a pretty large effect for a pretty small intervention" Schwizgebel says. Psychologist Nina Strohminger at the University of Pennsylvania, who was not involved in the study, says she wants the effect to be real but cannot rule out some unknown confounding variable. And if real, she notes, it might be reversible by another nudge: "Easy come, easy go".
Schwitzgebel suspects the greatest impact came from social influence —— classmates or teaching assistants leading the discussions may have shared their own vegetarianism, showing it as achievable or more common. Second, the video may have had an emotional impact. Least rousing, he thinks, was rational argument, although his co-authors say reason might play a bigger role. Now the researchers are probing the specific effects of teaching style, teaching assistants' eating habits and students' video exposure. Meanwhile, Schwitzgebel — who had predicted no effect—will be eating his words.
Eric Schwitzgebel suspects that the students change in behavior____.

A.can bring psychological benefits
B.can be analyzed statistically
C.is a result of multiple factors
D.is a sign of self-development

答案： C

本题解析：

Schwitzgebel suspects the greatest impact came from social influence —— classmates or teaching assistants leading the discussions may have shared their own vegetarianism, showing it as achievable or more common. Second, the video may have had an emotional impact. Least rousing, he thinks, was rational argument, although his co-authors say reason might play a bigger role. 施维茨格贝尔怀疑，最大的影响来自于社会影响——同学或助教主导的讨论可能分享了他们自己的素食主义，表明这是可以实现的或更常见的。其次，这段视频可能会有情感上的影响。他认为，影响最小的是伦理课程内容本身，尽管他的同事认为，理论课程内容本身可能会发挥更大的作用。B正确。他认为学生行为的改变来自很多因素的影响。

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