Answer:
x = oxygen
Explanation:
Food and water is essential to life at cellular level because this water is responsible for making food with the help of CO2 during photosynthesis in plant and this food provides energy to the cell and support the life of plant cell. In an animal cell, H2O helps in releasing waste product from cell and provide a medium for reactions to occur.
Apart from food and water oxygen is also required to support life because oxygen is required by cells to oxidize food and release energy from food so this energy is used to perform metabolic function of cells that support cell life.
