As is used in Paragraph 4, the phrase 'a control group' refers to ______. A.people working at the Oregon Department of Health B.people investigating at the Mulmomah County Health Department in Oregon C.people serving as a standard of comparison for checking test results D.people involved in passing legislation banning smoking in eating establishments
A.A.people B.people C.people D.people
【参考答案】
C 解析：这是一道细节题。题干中“a control group'’出现在第四段第一句，“The authors......