POP3与IMAP4是电子邮件系统中两种常用的协议。POP3与IMAP4的主要区别是（）。
A．POP3只传送邮件标题，而IMAP4还要传送邮件正文
B．POP3只传送有无邮件的信息，而IMAP4还要传送有多少邮件的信息
C．POP3直接将邮件正文传送到本地，而IMAP4在传送后还要删除服务器上的邮件
D．POP3直接将邮件概要及正文传送到本地，而IMAP4只先传送邮件概要不传正文
参考答案：D
解析：
对于第3邮局协议(POP3)，用户从POP3服务器读取邮件后，服务器缺省将该邮件删除。而对于第4版Internet消息访问协议(IMAP4)将邮件传送到本地主机后，并不永久保存到本地主机上，也不从服务器删除相关邮件。
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| I watched as my little brother was caught in the act. He was sitting in the comer of the living room, a 1 in one hand and my father's hymnbook (赞美诗集) in the other. As my father walked into the room, my brother cowered slightly (轻微地畏缩). He sensed that he had done something 2 . I could see that he had 3 my father's new hymnal and scribbled (乱涂) in it. Now he was waiting for his punishment. For my father, books were knowledge. They were important to him. And yet he loved his children. What he did next was 4 . Instead of punishing my brother, he sat down, took the pen from my brother's hand, and then wrote in the book himself, alongside the scribbles John had made:" 5 work,1959, age 2. How many times have I looked into your beautiful face and into your warm eyes looking up at me and 6 Cod for the one who has now scribbled in my new hymnal. You have made the book sacred (神圣的), as have your brother and sister." "Wow," I thought. "This is 7 ?" The years and the books came and went. Our family experienced what all families go through and perhaps a little bit more. But we always knew our parents 8 us and that one of the proofs (证明) of their love was the hymnal by the piano. Dad taught us about 9 really matters in life: people,not objects; tolerance (宽容), not judgment; love, not anger. Now I, too, am a father. But unlike my father,l do not wait for my daughters 10 to take books from my bookshelf and scribble in them. From time to time I take one down, and give it to one of my 11 to scribble in. And as I look at their artwork, I think about my father and the 12 he taught me. | ||||
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