The key factor in the success of these countries ( along with high literacy, which contributed to it ) was their ability to adapt to the international division of labor determined by the early industrializers and to stake out areas of specialization in international markets for which they were especially well suited. (TPO18, 50)

The key factor ( in the success of these countries) ( alongwith high literacy, which contributed to it) was their ability ( to adapt to the international division of labor) (determined by the early industrializers) and (to stake out areas of specialization in international markets) (for which they were especially well suited.)(TPO18, 50)

分析：

这个句子的主干就是：

The key factor was their ability

后面两个不定式的并列：

(to adapt to the international division of labor determined by the early industrializers)

and

(to stake out areas of specialization ininternational markets for which they were especially well suited. )

修饰一：(in the success of these countries) ，介词短语，修饰the key factor

中文：在这些国家的成功中

修饰二：(along with high literacy, which contributed to it) ，介词短语，修饰these countries

中文：拥有促进他们成功的高文化水平

修饰三：(to adapt to the international division of labor) ，非谓语动词，修饰ability

中文：适应国际劳动分工

修饰四：(determined by the early industrializers)，非谓语动词，修饰the international division of labor

中文：早期工业化国家决定的

修饰五：(to stake out areas of specialization in international markets) ，非谓语动词，修饰ability

中文：领他们特别合适的国际市场中的专门领域

修饰六：(for which they were especiallywell suited.)，从句，修饰markets

中文：他们特别适合的托福口语计时器

参考翻译：

这些国家(拥有促进他们成功的高文化水平)成功的关键因素是他们有适应早期工业化国家决定的国际劳动分工的能力，以及占领他们特别合适的国际市场中的专门领域的能力。

这个句子的主要修饰成分就是从句、介词短语以及从句，大家务必想清楚，每一个修饰成分修饰的是什么，才能看清楚这个句子的结构。