The gas which keeps our earth warm is:

1. O₂
2. N₂
3. CO₂
4. Ne

The acid used in the laboratory preparation of carbon dioxide gas is:

1. dil. hydrochloric acid
2. conc. sulphuric acid
3. dil. sulphuric acid
4. conc. hydrochloric acid

The substance used in artificial respiration is:

1. carbon
2. carbon dioxide
3. carbogen
4. carbonization

The substance which can sublime is :

1. baking soda
2. marble
3. lime water
4. dry ice