What is the purpose of the NBAR protocol discovery？（） ["to build a Packet Description Language Module （PDLM） file to be used in protocol matching","to discover applications and build class maps for data classification","to look into the TCP or UDP payload and classify packets based on the content","to build a database of all application data that passes through the router and queue the data accordingly"]
单眼线索
简述游戏的主题。
弗里得曼认为，从长期看来，货币流通速度（）。 ["稳定可预测","易变难以预测","恒定不变","决定于利率水平"]
食品中不允许加入的添加剂有（） ["色素","既是食品又是药品的植物","防腐剂","非食品原料","微量元素"]
简述无彩色的定义及它给人的心理作用。
