So, to evaluate the risks of infection, the study team flew on 10 different ____ in the U.S. during the flu season. 未知类型：{'label': 'questionDesc', 'content': '请选择正确答案', 'isMemberControl': 0, 'type': 181} 未知类型：{'label': 'source', 'content': '2019年12月 四级 卷二 选词填空', 'isMemberControl': 0, 'type': 181} A: respond B: flights C: explorations
So, to evaluate the risks of infection, the study team flew on 10 different ____ in the U.S. during the flu season. 未知类型：{'label': 'questionDesc', 'content': '请选择正确答案', 'isMemberControl': 0, 'type': 181} 未知类型：{'label': 'source', 'content': '2019年12月 四级 卷二 选词填空', 'isMemberControl': 0, 'type': 181} A: respond B: flights C: explorations
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