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．complete

B．compound

C．simple

D．efficient

CRT无显示的机床不能动作，其故障原因有（）、（）。

A.CRT单元输人电压不正常

B.连接CRT单元的电缆接触不良

C.主印制线路板有问题

D.组成CRT单元的显示单元、调节单元等有问题

E.控制R0M板有问题