在TCP/IP 协议族中,应用层的各种服务是建立在传输层提供服务的基础上。下列哪组协议需要使用传输层的 TCP 协议建立连接?( )。
A. DNS、DHCP、FTP
B. TELNET、SMTP、HTTP
C. BOOTP、FTP、TELNET
D. SMTP、FTP、TFTP
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1、用图解直接法求离心泵工况点的步骤（并画出示意图），说明为什么离心泵特性曲线与离心泵装置的管道特性曲线的交叉点K即为离心泵装置的工况点？手写，绘示意图，拍照上传
Where does this conversation most likely take place?
A. In a motel.
B. In a restaurant.
C. In the post office.
D. In the railway station.
How long will the woman wait according to the man?
A. 15 minutes.
B. 5 minutes.
C. 10 minutes.
D. 50 minutes.
Why does the man apologize the first time?
A. Because he doesn’t recognize the woman.
Because the woman has a reservation.
C. Because there are no vacancies left.
D. Because he hurts the woman’s feeling.
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