出站色灯信号机显示（）灯光准许列车由车站出发、开往次要线路。（半自动闭塞区段）
A、一个绿色
B、两个绿色
C、一个月白色
D、两个月白色
参考答案：B
从所给的四个选项中，选择最合适的一个填入问号处，使之呈现一定的规律性（）
A.
B.
C.
D.
Multipurpose Internet Mail Extension (MIME) is a (71) document messaging standard in theInternet enviroment.With MIME，users can send (72) Email messages that include audio，video，graphices，and text to any other user of TC/IP network.Richtext information can also be (73) into messages.It defines the fonts，formats，and (74) features of a document sothe document can be easily (75) on many different types of systems.
A．complete
B．compound
C．simple
D．efficient
