下列属于高处作业落物事件原因的是（）。

A.物料放置位置不当

B.个人安全防护用品佩带不当，人员行为不当

C.防护网设置不到位

D.工具绑扎牢

When amendments are made to the Shipboard Oil Pollution Emergency Plan，the revisions must be submitted to the Coast Guard（）.

A.one month before the anniversary date of the plan

B.six months before the end of the approval period

C.and cannot be implemented without approval

D.and can be implemented without immediate approval as long as final approval is received within six months of submission