光缆通信系统年允许阻断时间为（）小时。

A.100

B.125

C.25

D.175

Multipurpose Internet Mail Extension (MIME) is a (46) document messaging standard in the Internet enviroment, with MIME, users can send (47) Email messages that include audio, video, graph-ices, and text to any other user of a TCP/IP network. Richtext information can also be (48) into messages. It defines the fonts, formats, and (49) features of a document so the document can be easily (50) on many different types of systems.

A．incorporated

B．filled

C．stored

D．flied