Explanation: Fire extinguishers commonly used in houses and offices contain water, potassium bicarbonate (KHCO₃), and fluorocarbons. These chemicals help in extinguishing fires by cooling, cutting off oxygen supply, and preventing the spread of flames without leaving harmful residues.

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: 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 biosphere is the global sum of all ecosystems — it encompasses every region of Earth where living organisms are found. It includes portions of the lithosphere (land), hydrosphere (water), and atmosphere (air) that support life. The biosphere extends from deep ocean trenches to the lower layers of the atmosphere where microorganisms can survive.

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: 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: Ecology is a branch of biology that deals with the relationships of living organisms with one another and with their physical surroundings. It examines how organisms adapt to their environment, how energy flows through ecosystems, and how matter cycles within the biosphere. The term “Ecology” was first coined by Ernst Haeckel in 1866.

Explanation: The sex of a newborn baby is determined by the chromosome inherited from the father. Humans have 23 pairs of chromosomes — 22 pairs of autosomes and one pair of sex chromosomes. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The mother always contributes an X chromosome, but the father can contribute either an X or a Y. If the sperm carrying an X chromosome fertilizes the ovum, the child will be a girl (XX); if the sperm carries a Y chromosome, the child will be a boy (XY).