Explanation: Dakshin Gangotri is India’s first scientific research station established in Antarctica in 1983–84. It was set up by the Indian Antarctic Programme under the National Centre for Polar and Ocean Research (NCPOR). Located about 2,500 km from the South Pole, it served as a base for scientific studies related to glaciology, meteorology, and environmental sciences. Though it is now buried under ice and functions as a supply base, it marked India’s permanent presence in Antarctica. Later stations include Maitri (1989) and Bharati (2012).

Brown is not seen in a rainbow. A natural rainbow displays seven distinct colours — Violet, Indigo, Blue, Green, Yellow, Orange, and Red (VIBGYOR). These colours appear due to the dispersion of sunlight by water droplets in the atmosphere, but brown is not part of the visible spectrum formed by dispersion.

• Yellow, Green, Red: All are part of the seven colours of the rainbow.

Explanation: Teflon, also known as polytetrafluoroethylene (PTFE), is the polymer used in making non-stick kitchenware. It has a very low coefficient of friction and is resistant to heat and chemicals, which prevents food from sticking to cookware surfaces.

Explanation: The pale yellow color of normal human urine is due to the presence of a pigment called Urochrome. It is produced from the breakdown of hemoglobin in red blood cells. The intensity of the color depends on the concentration of the urine — darker yellow indicates concentrated urine, while very pale or colorless urine suggests dilution due to high water intake.

Explanation: Red light is used as a stop signal because it has the longest wavelength among visible colors, allowing it to scatter the least and remain visible from a greater distance, even in fog, rain, or dust. This ensures better visibility and safety on roads.

Explanation: PVC (Polyvinyl Chloride) is an example of a thermoplastic. Thermoplastics soften on heating and can be reshaped multiple times without undergoing any chemical change. In contrast, Bakelite and Melamine are thermosetting plastics that become hard and rigid after heating and cannot be remolded.

Explanation: A monitor is an output device that displays text, images, and videos generated by the computer. It allows users to visually view the processed data. Common types of monitors include LCD, LED, and OLED screens.

Explanation: Vitamin K is produced by gut bacteria (Escherichia coli) in the large intestine. It plays a vital role in the synthesis of prothrombin, a protein essential for normal blood clotting. Although some of it is obtained from food (like leafy vegetables), intestinal bacteria supply a significant portion of the body’s requirement.

Explanation: Nitrogen is an essential nutrient for plants, used in the synthesis of amino acids, proteins, nucleic acids, and chlorophyll. Plants absorb nitrogen from the soil primarily in the inorganic forms of nitrate (NO₃⁻) and nitrite (NO₂⁻). Urea, when applied as fertilizer, is first converted by soil bacteria into ammonia (NH₃) and then into nitrates through nitrification before being absorbed by roots.

Key Steps:

• Ammonification: Conversion of organic nitrogen (from dead plants/animals) into ammonia.
• Nitrification: Conversion of ammonia into nitrites and then nitrates by bacteria like Nitrosomonas and Nitrobacter.
• Assimilation: Uptake of nitrates by plants to form amino acids and proteins.