Answer:
Smallpox has had a major impact on world history, not least because indigenous populations of regions where smallpox was non-native, such as the Americas and Australia, were rapidly decimated and weakened by smallpox. During the 18th century the disease killed an estimated 400,000 Europeans each year, including five reigning monarchs, and was responsible for a third of all blindness. After successful vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the global eradication of smallpox in December 1979. Smallpox is one of two infectious diseases to have been eradicated.
Explanation:
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The soil that occurs in regions with extreme wet and dry seasons is known as "black soil."
Black soil:
- Chernozem is another name for black soil.
- It is largely composed of humus, phosphoric acid, phosphorus, and ammonia.
- Exceptionally small or clay-like particles constitute black soils.
- Deep gaps form during warmer weather, resulting in appropriate aeration.
Black soil characteristics include:
- It is extremely fertile and has a clay-like texture.
- At 25°C, the pH of black soil ranges from 7.2 to 8.5.
- The soil has high levels of potash, calcium, and magnesium but low levels of nitrate and phosphate.
- It is often soft when damp but hardens as it dries.
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