气体滑渗
参考答案：气渗流时，在固体孔壁上的速度不为零的现象，在气体分子的平衡自由行程与孔隙大小的数量级大致相当时，它对气渗流有明显影响。
根据现行《火灾自动报警系统设计规范》，火灾探测器的传输线路和50V以下供电控制线路，应采用电压等级不低于（）的铜芯绝缘导线或铜芯电缆
A.交流30V
B.交流250V
C.直流30V
D.交流120V
Darth Corporation’s most recent income statement shows net sales of $ 6000, and Darth’s marginal tax rate is 40 percent. The total expenses reported were $ 3200, all of which were paid in cash. In addition, depreciation expense was reported at $ 800. A further examination of the most recent balance sheets reveals that accounts receivable during that period increased by $1000. The cash flow from operating activities reported by Darth should be:
A．
B．
C．
