单项选择题 规定怎样将计算机连接到Internet邮件服务器和下载电子邮件的协议是        。 A、SMTP B、POP3 C、ARP D、IMAP

单项选择题 根据Document doc=new News();可以判断选项（ ）语法上是错误的。

单项选择题 The Tang Dynasty was an era of extensive cultural exchange betweenChina and the world. The products and artifacts of the ancientcivilizations in the world gathered in ( ).