Explanation

• Nitrogen (N₂) → 78%

Additional information:

• Oxygen (O₂) → 21%
• Argon (Ar) → 0.93%
• Carbon dioxide (CO₂) → 0.04% (approximately)
• Other gases → Trace amounts

Last verified on 28-06-2026

Explanation

• The primary component of natural gas is methane (CH4).
• Making up 70% to 90% or more of its composition.
• It is a colorless, odorless, and highly flammable hydrocarbon gas.
• Characteristics: It is a fossil fuel, often found in rock formations alongside oil or on its own. 

Last updated question 15 March2026

Explanation

• Smog is a combination of smoke and fog.
• The word smog is formed from smoke + fog.
• It is a type of air pollution that reduces visibility and can harm human health.
• Smog is commonly associated with vehicle emissions and industrial pollutants.

Last verified on 06-10-2026

Explanation

• The troposphere is the lowest layer of the atmosphere.
• Most weather phenomena occur in this layer.
• Clouds, rain, storms, and winds mainly occur here.
• It extends roughly 8–15 km above Earth’s surface.

• Mesosphere: About 50–85 km; most meteors burn up here.
• Ionosphere: Region with many charged particles; important for radio communication and auroras.
• Stratosphere: About 12–50 km; contains the ozone layer.

Explanation

• Nicolaus Copernicus proposed the heliocentric model.
• Heliocentric means the Sun is at the center.
• Earth and other planets revolve around the Sun.
• Proposed in the 16th century.
• Ptolemy supported the geocentric model (Earth-centered).