Answer:
Option-A
Explanation:
With the evolution of oxygen on Earth, the anaerobic organisms evolved themselves to use oxygen but still, 75% of the anaerobic organism died at the time when oxygen evolved.
The oxygen was used as the electron acceptor in the last phase of the electron transport taking place in the mitochondria. The oxygen binds with the low energy electron at the end of the chain reaction and with the protons and forms the water molecule. This water is known as the metabolic water.
Thus, Option-A is the correct answer.
