Explanation: The gas used for artificial ripening of green fruits is ethylene (C₂H₄). Ethylene is a natural plant hormone that regulates fruit ripening by stimulating the conversion of starches into sugars, making the fruit softer and sweeter. In artificial ripening, ethylene gas is introduced in controlled amounts to uniformly ripen fruits such as bananas, mangoes, and tomatoes. However, the use of harmful chemicals like calcium carbide for ripening is banned because it produces toxic substances like acetylene.

Explanation: The longest day in the Southern Hemisphere occurs on 22nd December, which marks the Summer Solstice in that hemisphere. On this date, the South Pole is tilted toward the Sun, resulting in longer daylight hours and shorter nights. Conversely, at the same time, the Northern Hemisphere experiences its winter solstice—the shortest day and longest night of the year. After 22nd December, the days in the Southern Hemisphere gradually begin to shorten.

The Taj Mahal is threatened primarily due to sulphur dioxide (SO₂) pollution. When sulphur dioxide released from nearby industries and vehicles mixes with moisture in the air, it forms sulphuric acid, leading to acid rain. This acid rain reacts with the white marble of the Taj Mahal, causing it to turn yellow and deteriorate — a phenomenon known as “Marble Cancer.”

Other options (for context)

• Carbon dioxide: Contributes to global warming but does not directly damage marble.
• Carbon monoxide: Harmful to health but has minimal effect on marble structures.
• Water vapour: Naturally present in the atmosphere and not harmful to monuments.

The full form of LAN is Local Area Network. It is a network that connects computers and devices within a limited geographical area such as a home, office, school, or building. LANs enable data sharing, resource sharing (like printers or internet connections), and communication between connected devices. Common technologies used in LANs include Ethernet and Wi-Fi.

Other options (for context)

• Line Area Network: Incorrect — not a recognized networking term.
• Linear Area Network: Incorrect — there is no such standard network type.
• Land Area Network: Incorrect — misinterpretation of LAN abbreviation.

Explanation: The chemical name of baking powder is sodium bicarbonate (NaHCO₃), also known as baking soda. It is a mild alkali used in cooking and baking as a leavening agent. When heated or mixed with an acid (like vinegar, lemon juice, or cream of tartar), it decomposes to release carbon dioxide gas (CO₂). The bubbles of CO₂ make the dough rise and become soft and spongy. In commercial baking powder, sodium bicarbonate is often mixed with a weak acid and a drying agent.

Explanation: A modem (short for modulator-demodulator) is a device that enables computers to communicate with each other over telephone lines. It converts digital signals from a computer into analog signals for transmission and then back into digital form at the receiving end.

Explanation: Wind energy is a clean and renewable source of energy that does not cause environmental pollution. It is generated by converting the kinetic energy of moving air into mechanical or electrical energy using wind turbines. Unlike fossil fuels such as coal or mineral oil, wind energy does not release carbon dioxide, sulfur dioxide, or other greenhouse gases. It is, therefore, a pollution-free and sustainable source of power, widely used for electricity generation in wind farms.

Explanation: Trichology is derived from the Greek word “trikhos”, meaning hair. It is a specialized field within dermatology that focuses on the structure, function, and diseases of hair and scalp. Trichologists diagnose and treat conditions such as hair loss (alopecia), dandruff, scalp infections, and hair shaft disorders.

Common Hair Disorders Studied in Trichology:

• Alopecia: Hair loss due to genetics, stress, or autoimmune disorders.
• Dandruff (Seborrheic dermatitis): Scalp condition causing flaking and itching.
• Tinea capitis: Fungal infection of the scalp (ringworm).