No, it is a mixture of nine different gases. Nitrogen, Oxygen, Argon, Carbon dioxide, Neon, Helium, Krypto, Xenon, and Hydrogen.

Carbon mono oxide is not a permanent part of the earth’s atmosphere. It is a pollutant but not a permanent part of the atmosphere.

No, water vapour is a variable gas in the atmosphere, which decreases with altitude.

This is the correct answer. Dust particles are generally concentrated in the lower layers of the atmosphere. Convectional air currents may sometimes transport them to great heights.

This is the correct answer, as statements a and b are the correct statements.

Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.

This statement is incorrect. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface.

The troposphere is the lowermost layer of the atmosphere.

The column of atmosphere is divided into five different layers depending upon the temperature condition.

The ionosphere or thermosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer.

The stratosphere is found above the tropopause and extends up to a height of 50 km. One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.

The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km.

This is the correct answer. The main elements of atmosphere, which are subject to change and also influence human life on earth, are temperature, pressure, winds, humidity, clouds and precipitation.

Yes. nitrogen constitutes 78.08% of the atmospheric air.

This is largely responsible for the green house effect.The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels. This has also increased the temperature of the air.