developed countries should help developing countries. ...why

简单的说：共同发展,拉小差距,维持和平,避免势强凌弱,再次野心扩张,世界失去平衡的结果是战争
利益驱使,更小的资本注入,其实是资本侵略,自然资源侵害,廉价劳动力以及文化蚕食. 两个方面来考虑
In simple terms: common development, widening gap between the small, peacekeeping, to avoid potential bullying, ambitious expansion again, the world has lost balance is the result of the war
Driven by interests, but also a small capital injection, is the capital of aggression, abuse of natural resources, cheap labor, as well as cultural eroded. Two aspects to consider

发达国家应该帮助发展中国家.

发达国家应该帮助发展中国家

因为这是一个全球化社会你要更好地发展就不能不管发展中地区。

发达国家应该帮助发展中国家...为什么

Such a big question,hard to answer...

这是发达国家的义务,因为要建设一个共同繁荣的世界.
这里面有政治意义,缩小差距,避免战争,维护和平.