Hepatitis is a disease that primarily affects the liver. It is characterized by inflammation of the liver tissues and can be caused by viral infections (such as Hepatitis A, B, C, D, and E viruses), excessive alcohol consumption, toxins, or autoimmune conditions. Symptoms include jaundice (yellowing of the skin and eyes), fatigue, nausea, and abdominal pain. Severe or chronic hepatitis can lead to liver failure or cirrhosis if left untreated.

Other options (for context)

• Pancreas: Affected by diseases like pancreatitis or diabetes, not hepatitis.
• Spleen: Involved in blood filtration and immunity, not affected by hepatitis.
• Small intestine: Responsible for digestion and absorption of food, not linked to hepatitis.

Explanation: In 1643, Italian scientist Evangelista Torricelli invented the barometer, an instrument used to measure atmospheric pressure. His mercury barometer demonstrated that air has weight and that atmospheric pressure can support a column of mercury in a glass tube.

Explanation: The plasma membrane in eukaryotic cells is mainly made up of a phospholipid bilayer arranged in a fluid mosaic model. Each phospholipid molecule consists of a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails. This arrangement creates a semi-permeable barrier that regulates the movement of substances into and out of the cell. Embedded proteins, cholesterol, and carbohydrates contribute to transport, signaling, and membrane stability.

Explanation: The tusks of elephants are actually modified second upper incisors. They are made primarily of dentine, commonly known as ivory, and covered by a thin layer of enamel at the tip (which wears off with time). Tusks grow continuously throughout the elephant’s life and are used for digging, lifting objects, stripping bark, defense, and dominance displays.

Note: Both male and female African elephants have tusks, whereas in Asian elephants, tusks are generally present only in males.

Composition: Tusks are composed of dentine (ivory) with fine concentric growth lines, and they grow from sockets in the skull.

Explanation: The burning of a candle is a chemical change because new substances such as carbon dioxide, water vapour, and heat energy are produced during the reaction between wax and oxygen. This change is irreversible and results in a permanent alteration of the chemical composition of the material. In contrast, melting of wax and vapourisation of water are physical changes since no new substances are formed and the process can be reversed by cooling.

Xylem is a type of vascular tissue in plants responsible for the transportation of water and dissolved minerals from the roots to the stems and leaves. The upward movement of water through xylem vessels occurs due to processes like transpiration pull, root pressure, and capillary action. Xylem also provides mechanical support to the plant.

Other options (for context)

• Food: Transported by phloem, not xylem.
• Nutrient: Minerals are carried along with water but the primary function of xylem is water transport.
• Both food and water: Incorrect — only phloem transports food; xylem transports water.

Explanation: The terms Dolby B and Dolby C refer to noise reduction circuits used in tape recorders and sound systems. These technologies reduce background hiss and unwanted noise during playback and recording, thereby improving the overall sound quality.

Explanation: Stars appear to twinkle at night due to the refraction of light by the Earth's atmosphere. As starlight passes through different layers of air with varying densities, its path bends continuously, causing the light’s intensity and position to appear to change, creating the twinkling effect.