If human blood becomes acidic (low pH), option 2 states that the oxygen-carrying capacity of haemoglobin is decreased. Haemoglobin is the protein in red blood cells that binds with oxygen and transports it throughout the body. In a slightly acidic environment, haemoglobin can`t bind effectively with oxygen, which leads to a reduced amount of oxygen being transported. This can result in a condition called acidosis.

When the blood pH drops, it indicates an excess of hydrogen ions (acidic) compared to hydroxide ions (alkaline). These excess hydrogen ions can interfere with the structure of haemoglobin and prevent it from functioning optimally. As a result, the ability of red blood cells to pick up oxygen in the lungs and deliver it to tissues and organs is impaired. This can lead to symptoms like fatigue, shortness of breath, dizziness, and confusion.

The other options are not correct in this context. Option 1 suggests that the oxygen-carrying capacity of haemoglobin would be increased, which is not the case in an acidic environment. Option 3 states that the number of red blood cells (RBC count) increases. However, the issue here is not the number of RBCs but the function of haem