Inhaling of oxygen and releasing of carbon dioxide to make our living is the process called as respiration. We know that, air is a mixture several gases like 78% of nitrogen, 21% of oxygen and several other gases with watervapour.
Hence, Oxygen is essential for respiration process.
A sentence has been given in Direct/Indirect Speech. Out of the four given alternatives, select the one which best expresses the same sentence in Indirect/Direct Speech.