Electronic mail, or mail, as it is known to its many fans, has been around for over two decades. Typically, email systems support five basic functions, as described below. (41) refers to the process of creating messages and answers. (42) refers to moving messages from the originator to the recipient. (43) has to do with telling the originator what happened to the message. Was it rejected Was it lost (44) incoming message is needed. So people can read their email. (45) is the final step and concerns what the recipient does with the message after receiving it.

（41）是（）

A.Composition

B.Transfer

C.Reporting

D.Displaying

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铸造支架组成中的网状连接体下述要求中正确的是

A．要有足够的强度

B．网状连接体的面积要比需要形成的塑料基托范围大

C．在前牙区设置网状连接体时，需要增设补强丝

D．网状连接体可用成品蜡网成型

E．网状连接体可用蜡线组合而成

F．网状连接体与黏膜之间应留有塑料位置