在超声波检测中，下列哪个频率的探头可获得相对最佳分辨率（） ["20kHz","30kHz","40kHz","50kHz"]
What is a characteristic of Network Time Protocol？（） ["NTP updates are sent in the timezone they are collected in，and the syslog server will adjust based on the input time.","NTP authentication verifies the source，not the recipient.","NTP authentication requires that the recipient has multiple strata clocks to ensure accuracy.","Secure NTP can be configured to use SHA-1 hashing，since NTP is very insecure.","A stratum 0 clock should be configured at the core of every network，so it can connect to an accuratetime source."]
自动化现代办公设备不包括（） ["机械照相机","速录机","传真机","数码速印机"]
同质性是总体的根本特征，是构成总体的（）。 ["前提条件","必要条件","充分条件","充要条件"]
明清时期社会经济继续发展的主要原因在于（）。 ["农业生产力进步的促进","封建生产关系调整的影响","商品经济繁荣的拉动","对外贸易扩大的刺激"]
如何理解设计美的文化性
