Everyday Science

The Earth's atmosphere contains approximately 21% oxygen by volume, which is essential for respiration in most living organisms. This is a well-established scientific fact.

The visible part of the ear is called the pinna, which is also referred to as the external ear. Therefore, both options A (External Ear) and B (Pinna) correctly describe the visible part of the ear, making option D (both A & B) the correct answer.

Carbohydrates are the body's primary and quickest source of energy because they are easily broken down into glucose, which cells use for fuel. Minerals and vitamins do not provide energy, and 'None of these' is incorrect.

All the options listed—Petrol, Kerosene, and Paraffin oil—are types of liquid fuels commonly used for combustion and energy purposes.

1 meter is equal to 100 centimeters because the prefix 'centi-' means one hundredth, so 100 centimeters make up 1 meter.

Common TV remote controls use infrared waves to transmit signals to the television. Infrared light is invisible to the human eye and is well-suited for short-range communication like remote controls.

The audio signals of television are transmitted using frequency modulation (FM) because FM provides better noise immunity and sound quality compared to amplitude modulation (AM).

Vitamin B-9 is commonly known as folate, which is essential for DNA synthesis and cell growth. The other options correspond to different vitamins with distinct functions.

Carbon dating, also known as radiocarbon dating, uses the radioactive decay of carbon-14 to determine the age of organic materials from the prehistoric period. It is the most common method for dating archaeological and geological samples up to about 50,000 years old.

A kilowatt-hour (kWh) is a unit of energy, representing the amount of energy consumed when a power of one kilowatt is used for one hour. It is not a unit of power, current, or time.