一个web资源（协议：//域名或IP地址：端口号）的访问由多个要素组成分别是域名、（ ）和端口号； A.
IP B.
MAC C.
TCP D.
UDP

单项选择题阀灵敏度式EPS，车速低时，电磁阀关闭。 A、正确 B、错误

单项选择题Before the Canton Fair, Jessica starts the training of business etiquette. It consists of ______ sessions and the training of greeting manners is in the _____ one. A、THREE， 1st B、THREE， 2nd C、FOUR， 1st D、FOUR， 2nd