The apples have fallen from the tree.

问题描述:

The apples have fallen from the tree.
苹果从树上掉下来.
· The dictionary fell off the desk.
字典从书桌上掉下来了.
同样的结构为什么用的介词不一样?from和off

苹果是长在树上的所以要用from
字典是放在桌子上的所以用off