undeveloped countries

例句：

1. 1. The undeveloped regions of Africa are rich in natural resources.
   非洲的未开发地区拥有丰富的自然资源。
2. 2. The government has invested heavily in developing the infrastructure of the country.
   政府已大力投资于该国基础设施的发展。
3. 3. The undeveloped economy of the region is expected to grow rapidly in the coming years.
   该地区的未发展经济预计将在未来几年内快速增长。