The author seems to______ that chemical pollutants cause the changes of boy: girl ratio at birth.
A．agree
B．deny
C．doubt
D．believe

A.
A．agree
B．deny
C．doubt
D．believe


【参考答案】

B
解析：推断题。由题干中的chemical pollutants定位至首段。末句指出“No one knows......

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