以宫底部的宫缩最强且最持久，向下逐渐减弱，宫底部收缩力的强度几乎是子宫下段的3倍。
参考答案：错
下列物质属于氧化物的是（ ）
A．02
B．CO
C．KCl03
D．CH3COOH
The law of diminishing returns states that for a given production process, as more and more of a resource (such as labor) are added, holding the quantities of other resources fixed:（）
A. cost declines at an increasing rate.
B. cost declines at a decreasing rate.
C. output increases at a decreasing rate.
