The correct option is (A) to fuel their chemical reactions
A lot of biochemical reactions occur per minute inside living cells and these reactions have to be sustained because the survival of living cells depend on them. For these reactions to proceed, energy is needed. This energy is usually obtained from the food which a living organism consumed. The mitochondria, which is the power house of the cell, is the one which convert the energy to the ATP form, which is usable by the cells.
