Answer:  Option B - Reflection of light by mirrors

Explanation:

• Optical telescopes primarily function based on the principle of reflection of light by mirrors.
• The primary mirror gathers and focuses light to form an image, which is then magnified by secondary mirrors or lenses.
• This reflective design allows telescopes to observe distant celestial objects with high clarity and resolution.
• While some telescopes use lenses (refracting telescopes), most modern optical telescopes use mirrors.

Answer:  Option A - Controlled blasting in mining

Explanation:

• Ammonium Nitrate (AN) is predominantly used in controlled blasting for mining operations.
• Its high nitrogen content makes it an effective explosive for breaking rock to access minerals like coal and iron ore.
• Additionally, AN is a crucial component in nitrogen-based fertilizers, enhancing soil fertility for agricultural purposes.

Its dual role in mining and agriculture underscores its significance in both industries.

Answer:  Option C - Extremely Large Telescope (ELT)

Explanation:

• The Extremely Large Telescope (ELT), situated in Chile, is recognized as the world's largest optical/infrared telescope.
• It is designed by the European Southern Observatory (ESO) and features a main mirror 39 meters in diameter.
• The ELT aims to enhance our understanding of the universe by enabling detailed observations of distant galaxies, exoplanets, and cosmic phenomena, surpassing the capabilities of other major telescopes like the Very Large Telescope (VLT).

Answer:  Option B - Large stone structures or burial monuments constructed during the prehistoric period

Explanation:

• In South India, "megaliths" refer to large stone structures used primarily for burial purposes and ceremonial functions during the prehistoric period.
• These structures include stone circles, dolmens, and menhirs, which were typically used to mark burial sites or serve as memorials.
• They are significant for understanding the cultural and social practices of ancient South Indian communities.

Answer:  Option D - North-East Region

Explanation:

• The North-East Region of India is renowned for its rich diversity of ornamental fish species, with over 195 indigenous varieties reported.
• This region, along with the Western Ghats, contributes significantly to India's ornamental fish exports.
• The variety and abundance of these species, primarily collected from rivers in the North-East, make it a key area for ornamental fishery, highlighting its ecological and economic importance in the sector.