语法大师来 下面关于副词修饰的几个问题 怎样判断副词修饰的是什么?

语法大师来 下面关于副词修饰的几个问题 怎样判断副词修饰的是什么?
副词可以修饰动词和副词短语,怎么判断到底是修饰的哪一个?比如：He is far behind me.He was strongly against slavery.It's well above my head.这3个句子中的副词分别修饰的是什么?怎么判断的?
It is the fourth leading cause of death worldwide..Let him out.这2句中的worldwide和out修饰的是什么?怎么判断的?
Part of the problem is that parts of Haiti haven't recovered from that massive earthquake back in January.这句话中的back修饰的是什么?怎么判断的?