Everyday Science

Leather is primarily made from collagen, a structural protein found in animal skin and connective tissues, which is processed to create leather.

Commercial aircraft usually fly in the troposphere, which is the lowest layer of the atmosphere where most weather phenomena occur and where air density is suitable for flight. The stratosphere is higher up and typically not used for commercial flights.

One mile is exactly 1609.34 meters, which is the standard conversion used internationally.

Vitamin A is found in animal-based foods like milk, eggs, butter, cheese, cream, and liver (option A), as well as in plant-based foods rich in beta-carotene such as broccoli, apricots, cantaloupe, carrots, sweet potato, and spinach (option C). Therefore, both A and C are correct sources of Vitamin A.

Thomas Edison is widely credited with inventing the practical and commercially viable incandescent light bulb, which revolutionized electric lighting.

As altitude increases, the temperature generally decreases due to the thinning atmosphere and lower air pressure, which causes air to cool.

Stars are primarily composed of gases, mainly hydrogen and helium, which undergo nuclear fusion to produce light and heat. Therefore, option A is correct as stars are essentially balls of gas.

A lactometer is an instrument used to measure the specific gravity (density) of milk, which helps determine its purity and quality. It is not used for ships or honey.

When water vapor cools below the dew point temperature, it condenses into liquid water droplets. This process is called condensation, which leads to the formation of dew, fog, or clouds.

Boiling an egg causes chemical changes in the proteins, denaturing them and changing their structure irreversibly, which classifies it as a chemical change rather than a physical one.