Explanation: Haemoglobin is a complex iron-containing protein found in red blood cells (RBCs). It binds with oxygen in the lungs to form oxyhaemoglobin and releases it in tissues where oxygen levels are low. It also helps transport carbon dioxide from tissues back to the lungs. This oxygen-carrying property makes haemoglobin the essential respiratory pigment in humans and most vertebrates.

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.

Metrology is the science of measurement. It deals with the establishment of units of measurement, their standards, and the development of new measuring methods and instruments. Metrology ensures accuracy and consistency in measurements across scientific research, engineering, manufacturing, and trade. It is broadly classified into three types — scientific metrology, industrial metrology, and legal metrology.

Other options (for context)

• Weather: The study of weather and atmosphere is called Meteorology, not Metrology.
• Distance: Measuring distance is just one aspect of metrology, not its entire scope.
• None of these: Incorrect — metrology specifically refers to measurement science.

Explanation: Carbon monoxide (CO) is a colorless, odorless, and highly poisonous gas. When inhaled, it competes with oxygen for binding sites on the haemoglobin molecule in red blood cells. CO has approximately 200–250 times greater affinity for haemoglobin than oxygen. As a result, it forms a stable compound called carboxyhaemoglobin (HbCO).

This compound prevents haemoglobin from carrying oxygen to body tissues, leading to oxygen deprivation (hypoxia). Prolonged exposure to CO can cause headache, dizziness, nausea, unconsciousness, and even death due to suffocation.

Chemical Reaction:

Hb + CO → HbCO (Carboxyhaemoglobin)

Explanation: Gamma rays are the most dangerous type of radiation because they have very high energy and strong penetrating power. They can pass through most materials, including human tissue, and may cause serious cellular and genetic damage. Proper shielding with dense materials like lead is required for protection.

Explanation: Although most non-metals do not conduct electricity, graphite is an exception. In graphite, each carbon atom is bonded to three others, leaving one free electron that moves freely between layers, allowing it to conduct electricity efficiently.

Explanation: Ringworm (also known as Dermatophytosis or Tinea infection) is a fungal skin disease. It appears as red, circular, itchy patches on the skin, scalp, or nails. Despite its name, it is not caused by a worm but by a fungus that grows on keratinized tissues such as skin, hair, and nails. The disease spreads through direct contact with infected individuals, animals, or contaminated objects.

Common Types:

• Tinea capitis: Ringworm of the scalp
• Tinea corporis: Ringworm of the body
• Tinea pedis: Athlete’s foot (infection of feet)
• Tinea cruris: Jock itch (infection of groin area)

Explanation: Red light is used as a stop signal because it has the longest wavelength among visible colors, allowing it to scatter the least and remain visible from a greater distance, even in fog, rain, or dust. This ensures better visibility and safety on roads.

Explanation: Entomology is a branch of Zoology that focuses on the study of insects, including their structure, classification, behavior, ecology, and evolution. Insects make up more than 75% of all known animal species on Earth and play crucial roles in pollination, decomposition, and food chains. Scientists who study insects are known as entomologists.