The gas that damages the ozone layer is -

1. CFCs 

2. CO₂

3. CH₄ 

4. SO₂

What is the correct sequence of atmospheric layers starting from earth

(1) Stratosphere troposphere, mesosphere, thermosphere

(2) Troposphere, stratosphere, mesosphere, thermosphere

(3) Mesosphere, troposphere, stratosphere, thermosphere

(4) Thermosphere, mesosphere, stratosphere, troposphere

Incorrect statement among the following is: 

1. Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutant.

2. pH of drinking water should be between 6.5 and 8.5.

3. Concentration of dissolved oxygen below 6 ppm is good for the growth of fish.

4. Clean water would have a BOD value of less than 5 ppm.