The phenomenon in which atmospheric gases trap the heat radiations from the sun near the earth’s surface and keeps it warm is known as-

1. Natural greenhouse effect

2. Tyndall effect

3. Heating effect

4. Joule’s effect

CO gas is more dangerous than CO₂ gas because : 

1. CO is capable of forming a complex with haemoglobin (carboxyhemoglobin), that is more stable than the oxygen-haemoglobin complex. 

2. CO is capable of forming a complex with haemoglobin (carboxyhemoglobin), that is less stable than the oxygen-haemoglobin complex. 

3. CO₂ is capable of forming a complex with haemoglobin (carboxyhemoglobin), that is more stable than the oxygen-haemoglobin complex. 

4. CO₂ is capable of forming a complex with haemoglobin (carboxyhemoglobin), that is less stable than the oxygen-haemoglobin complex. 

Gases responsible for greenhouse effect are : 
1. Carbon dioxide (CO₂)
2. Ozone (O₃)
3. Nitrous oxide (N₂O)
4. All of the above.

... is not a greenhouse gas :-
1. Hydrogen
2. Carbon dioxide
3. Methane
4. Nitrous oxide or $N_{2}O$

In the absence of greenhouse gases -

Among the following gases, the one that is not a greenhouse gas is :

1. CO

2. O₃ 

3. CH₄

4. H₂O vapor