Given below are two statements. 

Statement I: Low pH facilitates the delivery of oxygen to vigorously contracting skeletal muscle fibres.

Statement II: Lactic acid produced during anaerobic respiration in skeletal muscle fibres leads to a decrease in pH.

In light of the above statements, choose the most appropriate answer from the options given below. 

Statement I is true. Blood delivers oxygen more readily to vigorously contracting skeletal muscles than to resting muscles. During exercise, muscles need more oxygen for energy production, so blood flow to active muscles increases to meet this demand.

Statement II is also true. Anaerobic respiration in skeletal muscles leads to a decrease in pH that facilitates the dissociation of oxygen from oxyhaemoglobin. During intense exercise, muscles may switch to anaerobic respiration, producing lactic acid and decreasing pH. This decrease in pH promotes the release of oxygen from haemoglobin, helping to supply oxygen to the active muscles. The dissociation of oxygen from the haemoglobin is also promoted by factors such as low pO₂, high pCO₂ and high temperature.