OXYGEN CYCLE

The atmosphere contains ________ of oxygen.

• 21 per cent

• 13 per cent

• 75 per cent

• None of these

Oxygen from the atmosphere is used up in processes, namely

• Combustion

• Respiration

• In the form of oxides of nitrogen

• All of these

The two forms of oxygen formed in the atmosphere are

• Water and ozone

• Ozone and oxygen

• Water and oxygen

• All of these

In the oxygen cycle, the movement of oxygen takes place within

• Atmosphere

• Biosphere

• Lithosphere

• All of these

The oxygen cycle is an example of the _______ cycle.

• Chemical

• Photosynthesis

• Biogeochemical

• None of these