Explanation: The speed of internet connectivity is expressed in Megabits per second (Mb/sec or Mbps). It indicates how much data is transferred per second over a network connection. One megabit equals 1,000,000 bits. Higher Mbps values mean faster internet speeds. For example, a 100 Mbps connection can transfer 100 million bits of data every second. Note that 1 byte = 8 bits, so internet speeds in Mbps differ from file sizes, which are usually measured in megabytes (MB).

Explanation: Gerontology is the branch of medical and biological science that deals with the study of aging and the diseases and problems specific to old age. It focuses on understanding the physical, mental, and social changes that occur in elderly individuals, as well as methods to promote healthy aging. Gerontology includes aspects of geriatrics, which specifically involves the medical care and treatment of elderly patients.

Explanation: Malaria is not caused by a virus; it is caused by a protozoan parasite of the genus Plasmodium. The disease spreads through the bite of an infected female Anopheles mosquito. The parasite enters the human bloodstream, infects liver cells, and then red blood cells, leading to recurring fever, chills, and anemia. In contrast, Smallpox, AIDS, and Flu are all viral diseases caused by the Variola virus, HIV, and Influenza virus respectively.

Graphite is used in pencils. It is a soft form of carbon that leaves a dark mark on paper due to its layered structure, where carbon atoms are arranged in sheets that slide easily over each other. Though commonly called “lead,” pencils actually contain graphite mixed with clay to adjust hardness.

• Silicon: Used in electronics, not pencils.
• Charcoal: Used in art drawing but not regular pencils.
• Phosphorous: Used in safety matches and fertilizers, not pencils.

Bioremediation is the process by which living organisms — mainly microbes, fungi, or plants — are used to remove or neutralize contaminants, pollutants, or toxins from soil, water, or air. These organisms break down harmful substances into less toxic or non-toxic forms, helping to clean up polluted environments naturally. It is an eco-friendly and cost-effective method for environmental restoration.

Other options (for context)

• Biotechnology: A broader field involving the use of living systems for industrial, agricultural, or medical purposes.
• Biodegradation: The natural breakdown of organic materials by microorganisms, but not necessarily aimed at pollution cleanup.
• Biomagnification: The accumulation of toxic substances in the food chain, opposite of pollution removal.

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.

Explanation: The Indian Space Research Organisation (ISRO) is headquartered in Bangalore (Bengaluru), Karnataka. It was established in 1969 under the guidance of Dr. Vikram Sarabhai, who is known as the father of the Indian space program. ISRO is India’s national space agency, responsible for space research, satellite launches, and planetary exploration. It developed major missions such as Chandrayaan (Moon mission), Mangalyaan (Mars Orbiter Mission), and PSLV & GSLV launch vehicles.

Explanation: The element hydrogen is common to all acids. Acids are substances that produce hydrogen ions (H⁺) or hydronium ions (H₃O⁺) when dissolved in water. This property gives acids their characteristic sour taste, the ability to turn blue litmus paper red, and to react with bases to form salts and water. Examples include hydrochloric acid (HCl), sulphuric acid (H₂SO₄), and nitric acid (HNO₃)—all of which release hydrogen ions in aqueous solution.

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.