新建或改扩建矿井中，运行10t及以上机车或3t及其以上矿车的轨道，应采用不低于（）kg/m的钢轨。
A.22
B.18
C.24
D.30
参考答案：D
引起行政事业单位固定资产减少的因素有（）。
A.报废
B.毁损
C.出售
D.投资转出
Holding the quantity of labor constant, output increases as the quantity of capital increases, but at a decreasing rate. This phenomenon is most accurately described as:（）
A. diminishing marginal costs of capital.
B. diminishing marginal returns to labor.
C. diminishing marginal product of capital.
