What are the major organs of the respiratory system in humans?

Name the process by which plant parts like roots, stems, and leaves get oxygen required for respiration.

Name two animals which breathe through gills.

Which of the following statement$(s)$ is (are) correct?
$(i)$ Pyruvate can be converted into ethanol and carbon dioxide by yeast.
$(ii)$ Fermentation takes place in aerobic bacteria.
$(iii)$ Fermentation takes place in mitochondria.
$(iv)$ Fermentation is a form of anaerobic respiration.

State whether the following statement is true or false: Energy can be produced in cells without oxygen.

Name the energy currency in the living organisms. When and where is it produced?