Explanation

• The scientist who first discovered that the earth revolves around the sun was Copernicus.
• Earth's Rotational Theory:
  • Rotation can be defined as the spin of Earth on its own axis from west to east direction.
  • It must also be noted that the speed of rotation of the earth is not constant throughout latitudes.
    
  • It differs at different latitudes.

Explanation

Explanation

Measles is one of the world's most contagious diseases

It spread by contact with infected nasal or throat secretions (coughing or sneezing) or breathing the air that was breathed by someone with measles.

The virus remains active and contagious in the air or on infected surfaces for up to two hours.

Explanation

salt (NaCl), sodium chloride, a mineral substance of great importance to human and animal health, as well as to industry. 

Formula: NaCl

Molar mass: 58.44 g/mol

Melting point: 801 °C

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ND30-12-2022

ND5-07-2023

Explanation

White Blood Cells (WBCs), also known as leukocytes, are a vital part of the immune system.

They protect the body from infectious diseases and foreign invaders by identifying and eliminating pathogens.

Such as bacteria, viruses, and other foreign substances.

Explanation

Plastic is a synthetic material made from polymers.

It primarily derived from petrochemicals.

Plastic is entirely man-made.

It is widely used due to its versatility and durability.

Explanation

• Sunlight is a good source of vitamin D.
• When our skin is exposed to sunlight, it produces vitamin D.
• It is essential for bone health, immune function, and the regulation of calcium levels in the blood.

Explanation

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is produced when coal is burned without sufficient oxygen.

CO is highly toxic.

It can be deadly in high concentrations, as it displaces oxygen in the bloodstream.

Explanation

Explanation

Cooking is difficult in the mountains primarily due to low atmospheric pressure, which affects the boiling point of water. 

Decreased Pressure at High Altitude:

As altitude increases, the atmospheric pressure decreases because there is less air pushing down from above.

Lower Boiling Point:

Water boils when its vapor pressure equals the surrounding atmospheric pressure.

With lower pressure on mountains, water needs less heat to reach its boiling point, so it boils at a lower temperature than the 100°C (212°F) it does at sea level.

Slower Cooking:

Since food cooks based on temperature, boiling it in water that is not as hot (e.g., 92°C at 8,000 feet) means the cooking process takes significantly longer to achieve the same result as at sea level.