设备的保全方式主要分四类：定期保全、预防保全、事后保全、（）等.
A、维修保全
B、改良保全
C、定时保全
D、分工保全
参考答案：B
John is not a man to count on, and it is very likely that the work ____ by the time he arrives here.[ ]
A. is finished
B. has finished
C. will finish
D. will have been finished
事界
