Explanation: A parity bit is added to binary data in a computer system for error detection. It helps identify whether data has been altered during transmission or storage. The parity bit makes the total number of 1s either even (even parity) or odd (odd parity), allowing simple error checking.

Argon (Ar) is an inert gas, also known as a noble gas. It belongs to Group 18 of the periodic table, whose elements are characterized by complete outer electron shells, making them chemically unreactive. Argon constitutes about 0.93% of the Earth's atmosphere and is widely used in electric bulbs, welding, and in creating inert environments for chemical reactions.

Other options (for context)

• Hydrogen: Highly reactive and combustible gas.
• Nitrogen: Relatively less reactive but not inert; forms compounds like ammonia.
• Oxygen: Highly reactive gas essential for combustion and respiration.

Explanation: White blood cells (WBCs), also known as leukocytes, are responsible for producing the immune response in the human body. They defend against infections by attacking bacteria, viruses, and other foreign invaders, helping to maintain the body’s immunity.

Explanation: In computer programming, the term "Beans" is specifically associated with the Java programming language. A JavaBean is a reusable software component written in Java that can be manipulated visually in a builder tool. JavaBeans follow certain conventions such as having a no-argument constructor, providing getter and setter methods, and being serializable. They are widely used in Enterprise Java applications for data encapsulation and to promote modular, reusable code.

Explanation: An F1 (Formula One) car is primarily made of carbon fibre, a lightweight yet extremely strong and durable material. Carbon fibre provides high strength-to-weight ratio, excellent rigidity, and improved safety — essential for achieving high speeds and ensuring driver protection in racing conditions.

Explanation: The human retina contains two types of photoreceptor cells — rods and cones. Cones are concentrated in the central part of the retina (fovea) and are sensitive to different wavelengths of light — red, green, and blue. These enable colour vision and visual acuity in bright light. Rods, on the other hand, function in dim light and provide black-and-white vision.

Explanation: The sour taste of a lemon is due to the presence of citric acid. Citric acid is a weak organic acid found naturally in citrus fruits such as lemons, oranges, and limes. It gives them their characteristic tangy flavor and also acts as a natural preservative.

Explanation: The ATM (Automated Teller Machine) was invented by John Shepherd-Barron in 1967. He designed the first cash dispensing machine, which was installed by Barclays Bank in London, UK. The first ATM used special paper vouchers impregnated with a radioactive compound instead of plastic cards. The idea revolutionized the banking sector by allowing people to withdraw money anytime without visiting a bank counter. Modern ATMs now use magnetic or chip-based cards, PIN authentication, and networked systems for secure transactions.

Explanation: Nitrogen (N₂) constitutes the major portion of the Earth's atmosphere by volume — about 78%. It is a colorless, odorless, and inert gas that plays a vital role in maintaining atmospheric stability and supporting life through the nitrogen cycle. Oxygen makes up about 21% of the atmosphere and is essential for respiration and combustion. Other gases like argon (~0.93%) and carbon dioxide (~0.04%) are present in much smaller amounts.