信息安全是指通过各种信息技术,保证在各种系统和网络中传输、交换和存储的信息的机密性、完整性和() ["时效性","真实性","客观性","长期性"]
韵母根据韵头情况可分几类?请举例具体加以说明?
凡与氧接触的管道和部件等均应()。 ["清除杂质","清除水份","清除油脂","不用进行处理"]
Northern Ireland,which takes up the northern fifth of Ireland,is a fourth political division of() ["the United Kingdom","Ireland","Scotland","Wale"]
简述元代催办制度的主要内容。
简述网点的定义及作用。