His grandfather _______ for thirty years.    [ ]

A. died                        

B. was head    

C. has been dead        

D. has died

大修工序一般分为“拆、修、装”三个阶段进行，其中“修”是指对设备进行清扫、检查、处理设备缺陷，更换易磨损部件，落实特殊项目的技术措施，这是检修的重要环节。