不可压缩气体流动时，下述论述中正确的为（） ["总压线、势压线及位压线总是沿程下降的；","总压线、势压线及位压线均可能沿程有升有降；","总压线及位压线总是沿程下降的，势压线沿程可能有升有降；","总压线沿程总是下降的，势压线与位压线沿程可能有升有降。"]
如果完全成本法期末存货吸收的固定性制造费用大于期初存货释放的固定性制造费用，则两种方法营业净利润的差额（）。
伤亡事故类别按《企业职工伤亡事故分类》（GB6441-86）进行分类，有（）种。 ["10","15","20","25"]
What are two reasons to implement H·323 gatekeepers？（） [" to eliminate the need for VoIP gateways"," to scale a VoIP installation with multiple gateways"," to provide call admission control and limit the number of simultaneous calls on the network "," to meet the requirement to control H·323 gateways on a LAN"," to accept call requests and reduce the load on the gateway"]
教育实验设计的主要内容包括（） ["研究假设","自变量、因变量、控制变量","实验处理","以上都是"]
战国时期两位最重要的诗人是（）和（）。
