The correct option is
C Providing oxygen to anaerobically respiring structures
Most microorganisms such as fungi and bacteria can grow and flourish in the complete absence of oxygen and is known as fermentation. Pasteur described that fermentation is directly associated with the growth of metabolism of living matter. He observed that the rate of fermentation was considerably higher under anaerobic conditions as compared to aerobic conditions. The inhibition of anaerobic breakdown of sugars into carbon dioxide and ethyl alcohol due to the presence of oxygen under aerobic conditions is known as Pasteur effect.
Thus, the correct answer is 'Providing oxygen to anaerobically respiring structures'.