The Green Revolution is associated with Agriculture. It refers to the period during the 1960s–70s when new technologies like high-yield variety (HYV) seeds, fertilizers, irrigation, and pesticides were introduced to boost food grain production, especially wheat and rice. It helped India achieve self-sufficiency in food production.

• Sericulture: Rearing of silkworms for silk.
• Fishery: Cultivation and harvesting of fish.
• Cultivation of bees: Known as apiculture, for honey production.

Explanation: Shadows are formed when an opaque object comes in the path of light. Opaque objects do not allow light to pass through them, causing a dark region called a shadow to form on the opposite side. Transparent and translucent objects allow light to pass fully or partially, so they form faint or no shadows.

The Moon takes about 27.3 days to complete one revolution around the Earth with respect to the stars (called the sidereal month). However, due to the simultaneous movement of the Earth around the Sun, the Moon takes approximately 29.5 days to complete one full cycle of phases (from new moon to new moon), known as the synodic month. This period is commonly rounded to 28 days in general usage.

Other options (for context)

• 45 days: Much longer than the Moon’s actual orbital period.
• 50 days: Incorrect — the Moon completes more than one revolution in this time.
• 65 days: Far too long compared to the real lunar cycle.

Explanation: PARAM 8000 is India's first supercomputer, developed in 1991 by the Centre for Development of Advanced Computing (C-DAC) under the leadership of Dr. Vijay Bhatkar. It marked India’s entry into high-performance computing and was capable of 1 GigaFLOP (one billion calculations per second).

Sound waves from a loudspeaker are produced by vibrations of its diaphragm. When an electric current passes through the speaker coil, it causes the diaphragm to move back and forth, creating compressions and rarefactions in the air. These pressure variations travel as sound waves to our ears.

• Frequency: Determines pitch but does not create sound.
• Pitch: A property of sound, not its cause.
• Amplitude: Determines loudness but not the origin of sound.

Explanation: Red light is used in traffic signals because it has the longest wavelength among all visible colors. Due to this property, it gets scattered the least and can travel the farthest through fog, rain, or dust, making it easily visible from a long distance and ideal for indicating ‘stop’.

The Abacus is considered the first calculating device in human history. It was invented around 2500 BCE and used in ancient civilizations such as China, Egypt, and Mesopotamia. The Abacus consists of beads that slide on rods or wires, representing numbers, and is used to perform basic arithmetic operations like addition, subtraction, multiplication, and division. It laid the foundation for modern computing and calculating tools.

Other options (for context)

• Calculator: A modern electronic device for computation, developed much later.
• Turing machine: A theoretical computational model proposed by Alan Turing in 1936.
• Pascaline: A mechanical calculator invented by Blaise Pascal in 1642, long after the Abacus.

Explanation: Vitamin B₁₂, also known as Cobalamin, is the only vitamin that contains a metal ion — cobalt (Co) — at its core. It plays a crucial role in red blood cell formation, DNA synthesis, and proper nervous system function. Deficiency of Vitamin B₁₂ leads to pernicious anemia and neurological disorders. It is found mainly in animal-based foods such as meat, eggs, milk, and fish, and is synthesized by certain bacteria.

Dynamite was invented by Alfred Nobel in 1867. He was a Swedish chemist, engineer, and industrialist who discovered that nitroglycerin could be stabilized by mixing it with an absorbent material like diatomaceous earth, making it safer to handle and transport. This invention revolutionized the mining and construction industries. In his later years, Alfred Nobel established the Nobel Prizes using the wealth he accumulated from his inventions.

Other options (for context)

• J. B. Dunlop: Invented the pneumatic rubber tyre.
• James Simons: A mathematician and hedge fund manager, not an inventor.
• Peter Hargreaves: Not related to any major scientific invention; possibly confused with James Hargreaves, who invented the Spinning Jenny.