Explanation: LCD stands for Liquid Crystal Display. It is a flat-panel display technology commonly used in televisions, computer monitors, calculators, and smartphones. LCDs use liquid crystals that modulate light to produce images when an electric current is applied.

Explanation: Aurora Borealis, also known as the Northern Lights, is a natural light phenomenon visible mainly in the northern hemisphere, near the Arctic regions. It occurs when charged particles from the solar wind interact with gases like oxygen and nitrogen in the Earth's upper atmosphere (ionosphere). These collisions release energy in the form of colorful lights, usually green, pink, red, or violet. A similar phenomenon in the southern hemisphere is called the Aurora Australis or Southern Lights.

Explanation: The blue colour of the sky is due to the scattering of sunlight by molecules and small particles in the Earth's atmosphere. Shorter wavelengths of light (blue and violet) are scattered more than longer wavelengths (red and yellow). Since our eyes are more sensitive to blue light, the sky appears blue.

Explanation: White Blood Cells (WBCs), also known as leukocytes, act as the body’s defense system. They protect the body against pathogens such as bacteria, viruses, and fungi. Different types of WBCs — like lymphocytes, monocytes, neutrophils, eosinophils, and basophils — have specialized roles in immunity. Because they “fight” infections, they are popularly called the ‘soldiers of the human body.’

The normal body temperature of a healthy human being is approximately 37 °C, which is equivalent to 98.6 °F. This temperature is maintained through a balance between heat production and heat loss in the body. The body’s thermoregulation is controlled by the hypothalamus in the brain to ensure proper functioning of enzymes and metabolic processes.

Other options (for context)

• 98.4 °C: Incorrect — the correct equivalent in Fahrenheit is 98.6 °F, not in Celsius.
• 14.5 °C: Much lower than the human body temperature — such a value would indicate hypothermia or death.
• 25 °C: Represents a mild room temperature, not body temperature.

Explanation: A fan provides a feeling of comfort during hot weather because it increases the rate of evaporation of sweat from our skin. As the perspiration evaporates rapidly due to moving air, it absorbs heat from the body, producing a cooling effect and making us feel more comfortable.

Explanation: Lysosomes are known as the ‘suicidal bags’ or ‘disposal units’ of the cell because they contain powerful hydrolytic enzymes capable of breaking down worn-out cell organelles, foreign substances, and even the entire cell when it becomes damaged or diseased.

Explanation: Vitamins are classified into two categories based on their solubility — fat-soluble and water-soluble. Vitamin C (ascorbic acid) and the B-complex vitamins are water-soluble, meaning they dissolve in water and are not stored in the body. Therefore, they must be consumed regularly through diet. Deficiency of Vitamin C causes scurvy, characterized by bleeding gums and delayed wound healing.

Explanation: Below the critical temperature, gases can be liquefied by applying pressure because the intermolecular forces of attraction between gas molecules become effective. These forces pull the molecules closer together, resulting in the formation of a liquid state.