PINAKA is an indigenously developed Multi Barrel Rocket Launch (MBRL) system designed and produced by the Defence Research and Development Organisation (DRDO) of India. It is capable of firing a salvo of rockets to deliver explosive warheads over large areas with high accuracy. Pinaka is primarily used by the Indian Army for long-range artillery support and has a range of up to 75 km in its upgraded version (Pinaka Mk-II).

Other options (for context)

• Anti-submarine torpedo and research vehicle: Refers to underwater weapon systems, not related to Pinaka.
• Aircraft carrier: A large naval vessel capable of carrying aircraft; Pinaka is not a ship.
• Guided missile frigate submarine warship: Refers to naval warships, not a land-based rocket launcher.

Explanation: The rarest blood type in the world is AB⁻ (AB negative). It is found in less than 1% of the global population. People with AB⁻ blood can receive red blood cells from all Rh-negative blood types, but they can donate only to other AB individuals.

Explanation: Sodium hydroxide (NaOH) is a base, so it does not turn blue litmus paper red. Instead, it turns red litmus paper blue. In contrast, lemon juice, acetic acid, and hydrochloric acid are acidic and turn blue litmus red.

The CPU (Central Processing Unit) is known as the brain of the computer. It performs all major operations such as processing data, executing instructions, and controlling other components. The CPU consists of two main parts — the Arithmetic Logic Unit (ALU) for calculations and the Control Unit (CU) for directing operations.

• ALU: Handles arithmetic and logic operations only.
• Memory: Stores data and instructions, but doesn’t process them.
• Control Unit: Directs the flow of data but works as part of the CPU.

Explanation: Sound waves are not electromagnetic waves; they are mechanical waves that require a material medium (like air, water, or solids) for propagation. In contrast, radio waves, X-rays, and visible light are electromagnetic waves that can travel through a vacuum.

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.

Explanation: The gastric glands in the stomach secrete gastric juice, which contains three main components — hydrochloric acid (HCl), pepsinogen, and mucus. Pepsinogen is the inactive form that is converted to pepsin by HCl. Pepsin is a powerful enzyme that digests proteins into smaller peptides in the acidic environment of the stomach.