A Hygrometer is an instrument used to measure the humidity (moisture content) in the atmosphere. It helps determine the percentage of water vapor present in the air, which is essential for weather forecasting, climate studies, and maintaining controlled environments in industries or laboratories. Some common types include the dry and wet bulb hygrometer and the digital hygrometer.

Other options (for context)

• Barometer: Used to measure atmospheric pressure.
• Anemometer: Used to measure wind speed.
• Thermometer: Used to measure temperature.

The physical quantity measured in kg·m/s² is Force. The SI unit of force is the Newton (N), which is defined as the force required to accelerate a mass of 1 kilogram by 1 meter per second squared. Mathematically, Force = Mass × Acceleration.

• Work: Measured in joules (N·m).
• Power: Measured in watts (J/s).
• Motion: Describes movement, not a measurable quantity in these units.

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.

Explanation: In an incompatible blood transfusion, the antibodies in the recipient’s plasma bind to the antigens on the donor’s RBCs. This causes the red blood cells to agglutinate (clump together) and eventually undergo hemolysis (bursting). The released hemoglobin can block kidney tubules and cause kidney failure, which can be fatal if untreated. This is why blood group compatibility testing (cross-matching) is essential before transfusions.

Example:

If a person with blood group B (having anti-A antibodies) receives blood from a person with group A (which has A antigens), the recipient’s anti-A antibodies will attack the donor’s RBCs, leading to agglutination.

Explanation: The star rating system seen on electrical appliances (like ACs, refrigerators, and fans) represents the energy efficiency of the product. It is issued by the Bureau of Energy Efficiency (BEE), under the Ministry of Power, Government of India. The more the number of stars (up to 5), the higher the energy efficiency — meaning the appliance consumes less electricity for the same performance. However, the star rating does not indicate the lifespan or the quality checks of the appliance.

The Ramsar Convention is an international treaty for the conservation and sustainable use of wetlands. Signed in 1971 at Ramsar, Iran, it aims to preserve wetlands as habitats for biodiversity, especially for migratory birds. It promotes wise use of wetland ecosystems through local and national actions.

• Mountain: Conserved under other ecological programs.
• Grassland: Managed under terrestrial biodiversity initiatives.
• Forest: Covered under the UN Forest Forum, not Ramsar.

Explanation: Amniocentesis is a medical diagnostic procedure used to determine the genetic and chromosomal makeup of a developing fetus. It involves the withdrawal of a small amount of amniotic fluid from the uterus using a fine needle. This fluid contains fetal cells that can be tested to identify genetic disorders such as Down’s syndrome and also to determine the sex of the fetus. However, using amniocentesis for sex determination is illegal in India under the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act to prevent female foeticide.

India’s first successful atomic device was tested at Pokhran in the Thar Desert of Rajasthan on 18th May 1974. The operation was code-named "Smiling Buddha" and was conducted by the Bhabha Atomic Research Centre (BARC) under the leadership of scientists like Dr. Raja Ramanna. This event marked India’s entry into the group of nuclear-capable nations.

Other options (for context)

• Bikaner: A city in Rajasthan, but no nuclear tests were conducted there.
• Barmer: Located near the Pakistan border, not the site of India’s nuclear test.
• Jaisalmer: Close to Pokhran geographically, but not the test location.

Bioremediation is the process by which living organisms — mainly microbes, fungi, or plants — are used to remove or neutralize contaminants, pollutants, or toxins from soil, water, or air. These organisms break down harmful substances into less toxic or non-toxic forms, helping to clean up polluted environments naturally. It is an eco-friendly and cost-effective method for environmental restoration.

Other options (for context)

• Biotechnology: A broader field involving the use of living systems for industrial, agricultural, or medical purposes.
• Biodegradation: The natural breakdown of organic materials by microorganisms, but not necessarily aimed at pollution cleanup.
• Biomagnification: The accumulation of toxic substances in the food chain, opposite of pollution removal.