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.

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: Alcohols are organic compounds composed of carbon (C), hydrogen (H), and oxygen (O). They are characterized by the presence of one or more hydroxyl (-OH) functional groups attached to a carbon atom. The general formula of alcohols is C_nH_2n+1OH. A common example is ethanol (C₂H₅OH), which is used in beverages, fuels, and sanitizers. The -OH group makes alcohols polar, soluble in water (especially lower alcohols), and reactive in many organic reactions.

John McCarthy is regarded as the father of Artificial Intelligence (AI). He coined the term “Artificial Intelligence” in 1956 during the Dartmouth Conference, which is considered the founding event of AI as a research field. McCarthy also developed the LISP programming language, one of the earliest languages used for AI programming. His contributions laid the foundation for modern AI research, machine learning, and robotics.

Other options (for context)

• Charles Babbage: Known as the “Father of the Computer” for designing the Analytical Engine.
• Lee De Forest: Invented the triode vacuum tube, which advanced early electronics.
• J. P. Eckert: Co-inventor of ENIAC, one of the first electronic general-purpose computers.

The Kyoto Protocol is an international agreement related to the environment, specifically aimed at reducing greenhouse gas emissions that contribute to global warming and climate change. It was adopted in Kyoto, Japan, in 1997 and came into force in 2005. The protocol set binding targets for developed countries to limit or reduce their carbon dioxide (CO₂) and other greenhouse gas emissions.

Other options (for context)

• Nuclear Power: Not the focus of the Kyoto Protocol; this relates to energy generation and atomic energy regulation.
• Trade: Covered under agreements like GATT and WTO, not the Kyoto Protocol.
• None of these: Incorrect — the Kyoto Protocol deals specifically with environmental protection.

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.

The Air Quality Index (AQI) is a numerical scale used to measure and report the quality of air in a particular area. It primarily indicates the level of air pollution and its potential impact on human health. The AQI is calculated based on concentrations of key air pollutants — including ozone (O₃), particulate matter (PM₂.₅ and PM₁₀), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), and carbon monoxide (CO). Higher AQI values indicate poorer air quality and greater health risks.

Other options (for context)

In medical terminology, USG stands for Ultrasonography. It is a diagnostic imaging technique that uses high-frequency sound waves to create images of internal organs, tissues, and developing fetuses. USG is commonly used in obstetrics, cardiology, and abdominal examinations as it is safe and non-invasive.

• Undersized gland: Not a recognized medical term.
• Unsegmented gonads: Incorrect and unrelated to imaging.
• None of the above: Incorrect as option B is correct.