Answer:
They are home to 70 percent of the world's population.
Two-thirds of the people live in cities and earn their incomes from industry.
Explanation:
The term more-developed countries is linked to the concept of "developed country". Other terms to describe these countries are: "advanced country", "more economically developed country", "first world country", at it´s used to describe sovereign nations that have a developed economy and advanced technological infrastructure compared to other less industrialized nations. This concept also applies to Economies based on advanced technology and factories. For this reason, options 1 and 2 don't apply to "middle-income nations".
The term Middle-income countries is linked to the concept of "Developing Country". According to the World Bank, Middle Income Countries are home to 75% of the world’s population and 62% of the world’s poor. Also, they tend to have some characteristics in common, such as low levels of access to safe drinking water, sanitation and hygiene, energy poverty, low education levels, among others, so option 3 is incorrect as well.
Social change is very common in "Developing Countries", where rural populations migrate to the cities to work in the industries.
