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【单选题】35岁，孕39周，G1P0，无痛性阴道出血5h，1h前出现规律宫缩，阴道出血量约500ml，腹部检查ROA，胎头高浮，胎心160次／分，耻骨联合上可闻及与母体脉搏一致的吹风样杂音。该患者最恰当的处理是（）
A.
使用止血药
B.
行剖宫产
C.
等待自然分娩
D.
静脉点滴催产素
E.
人工破膜后头皮钳牵引
【单选题】Many people feel that human beings are responsible for the disappearance of some other animal species. While we may have hastened the disappearance of some, abundant evidence suggests mankind has had ...
A.
Human beings have hastened the disappearance of some.
B.
There was mass extinction long before humanity's time on Earth.
C.
Human beings'activities have had great impact on the earth.
D.
Many species have extinct since the human race came into being.
【单选题】边际产量递减规律所研究的问题是（ ）
A.
其他生产要素不变，一种生产要素变动时对产量的影响
B.
各种生产要素同时变动对产量的影响
C.
两种生产要素同时变动对产品的影响
D.
一种生产要素不变，其他生产要素变动时对产量的影响