Answer to Question 1
The four main categories of the world economies are categorized by annual per-capita income levels. Low-income economies which include India, Pakistan, and much of the sub-Saharan Africa. Lower middle income includes most Middle Eastern Countries, Latin American, Caribbean countries, the former Soviet countries and the most of the African countries. The upper middle income economies which are Latin American countries, Saudi Arabia, Malaysia, South Africa, Poland, Hungary, Czech and the Slovak Republic. The last category is the high-income economies such as Korea, Israel, Kuwait, Singapore and the United states.
Answer to Question 2
By allowing them to reduce the riskiness of the return on their wealth and by allowing the two parties to diversify their portfolios, i.e., to divide their wealth among a wider spectrum of assets, and thus reduce the amount of money placed on one specific asset.
Examples of hydrogen bonds
Major rivers throughout the world.
The Ancient Roman World
World Total Energy Consumption by Fuel Type
The World's Religions (4th Edition)
Main mechanism of carbon dioxide transport and exchange. A lesser amount of CO2 travels to the lungs