根据短文内容和首字母的提示，把文中所缺词语补充出来，使短文完整、正确、通顺。（每空限填一词，将其填写在文后相应便会2的横线上）

Did you know that tea, the most popular drink in the world (after water), was invented by accident?Although tea wasn't brought to the Western world u 小题1: 1610, this beverage was discovered over three thousand y小题2: before that. According to an ancient Chinese legend,the emperor Shen Nong discovered tea when he was b 小题3: drinking water over an open fire. Some leaves from a nearby bush fell into the water and remained there for some time. The emperor noticed that the leaves in the water produced a pleasant smell. L 小题4: he decided to taste the hot mixture. It was quite d  小题5: And in this way,one of the world's favorite drinks was invented.

端口号的目的是什么？（）

A、跟综同一网络中的不同会话

B、源系统使用端口号维持会话的有序，以及选择适当的应用

C、端系统依据其应用程序的使用情况，用端口号分配一个特定的会话

D、源系统产生端口号来预报目的地址