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: Unwanted or unsolicited e-mails sent in bulk are called spam. These messages often contain advertisements, phishing links, or malware. They clutter inboxes and can pose security risks. The term “spam” originated from a comedy sketch by Monty Python, where the word was repeatedly used, much like unwanted messages.

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: Ascorbic acid is not a member of the vitamin B complex; it is actually vitamin C. The vitamin B complex includes vitamins like thiamine (B₁), riboflavin (B₂), niacin (B₃), folic acid (B₉), and others that play important roles in metabolism and energy production.

Explanation: Kala-azar, also known as visceral leishmaniasis, is caused by the protozoan parasite Leishmania donovani. It is transmitted through the bite of the female Phlebotomus sandfly. The disease primarily affects the liver, spleen, and bone marrow, leading to symptoms such as fever, anemia, weight loss, and darkening of the skin. The term “Kala-azar” literally means “black fever.”

Explanation: The colour of the sky without an atmosphere would appear black. On Earth, the sky looks blue because molecules in the atmosphere scatter sunlight — a phenomenon called Rayleigh scattering. Shorter wavelengths of light (blue and violet) are scattered more than longer wavelengths (red). However, if there were no atmosphere to scatter sunlight, no light would be diffused in all directions, and the sky would appear completely dark or black, just as it does from the surface of the Moon or in outer space.

An Atom bomb works on the principle of nuclear fission. In this process, the nucleus of a heavy atom such as Uranium-235 or Plutonium-239 splits into two or more smaller nuclei when bombarded with a neutron. This splitting releases a tremendous amount of energy along with more neutrons, which further cause chain reactions — leading to a massive explosion.

Other options (for context)

• Chemical reaction: Produces far less energy; used in conventional explosives, not atomic bombs.
• Nuclear fusion: Powers hydrogen bombs (thermonuclear bombs), not atomic bombs.
• Atomic collision: General term — does not describe the chain reaction mechanism in fission.