B. The Hubble Space Telescope
The answer is a the nervous system
The nervous system is connected to your brain and controls each and every action in your body.
- Oxygen cycle is the cycle which maintains the level of oxygen in the atmosphere.
- Oxygen from the atmosphere is used up during combustion, respiration and in the formation of oxides of nitrogen.
- This oxygen is returned to the atmosphere by lithosphere.
- This forms the oxygen cycle in nature.
Hope you could get an idea from here.
Doubt clarification - use comment section.
D.
This is so since the average person (with activity) stores enough glycogen to last him 12 to 14 hours.
