1.The order to abandon ship was given.
the order 就是：abandon ship,命令就是弃船,它们是同位语而不是互相修饰的定语中心词关系
原句可写成：
The order that we should abandon ship was given.（that引导同位语从句）
The order which abandoned ship was given.(x)
引导词若在从句中充当主语,句子意思错误,变成主语命令为施动者,它去放弃船,原句本意为：弃船的命令已下达．
2.The man on the boat=the man who is on the boat
I want an apple to eat.
to eat 不定式充当目的状语
不定式是非谓语动词,是高考、中考的重要考点.