Polar stratospheric clouds facilitate the formation of :

Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : Polluted water may have a value of BOD of the order of 17 ppm.

Reason R : BOD is a measure of oxygen required to oxidise both the bio-degradable an non-biodegradable organic material in water.

In the light of the above statements, choose the most appropriate answer from the options given below.

The eutrophication of water body results in :

Some gases are responsible for heating of atmosphere (green house effect). Identify from the following the gaseous species which does not cause it.