-How did you make so rapid progress in your English?Do you have any secrets?

-No.Only __________ hard working.[ ]

A．in terms of  

B．in honor of

C．by means of  

D．on behalf of

某建筑公司承建的某面粉厂工地，厂房内有一预留洞口，原有盖板，整修地面时被拆掉，未及时恢复。冷某在拉车时，倒退着走与推车者边走边谈话，从预留洞口坠落，经抢救无效死亡。请判断下列事故原因分析的对错。

工人未戴好安全带。