Displacement of O2 from its respiratory pigment:

A. occur more rapidly in cold temp.
B. occur more slowly when Ph alkaline.
C. occur more slowly when O2 tissue level low.
D. none of these.

To determine the correct answer, let's break down each option and analyze the underlying processes involved.

A. Displacement of O2 from its respiratory pigment occurring more rapidly in cold temperatures: This statement is incorrect. In general, the dissociation or displacement of O2 from its respiratory pigment, such as hemoglobin in humans, is influenced by temperature. At higher temperatures, the dissociation occurs more rapidly because increased temperature favors the release of oxygen from the respiratory pigment.

B. Displacement of O2 from its respiratory pigment occurring more slowly when the pH is alkaline: This statement is correct. The pH of a solution affects the affinity of the respiratory pigment for O2. In an alkaline environment (high pH), the oxygen-binding capacity of the respiratory pigment increases, resulting in a higher affinity for O2. Consequently, with an increased affinity, the displacement of O2 from the respiratory pigment occurs more slowly.

C. Displacement of O2 from its respiratory pigment occurring more slowly when tissue O2 levels are low: This statement is incorrect. When tissue oxygen levels are low, it creates a concentration gradient. According to the principles of diffusion, substances tend to move from areas of higher concentration to areas of lower concentration. Therefore, in the presence of low tissue oxygen levels, O2 will be more readily released from the respiratory pigment to meet the demand of oxygen-deficient tissues. Consequently, the displacement of O2 from the respiratory pigment occurs more rapidly when tissue O2 levels are low.

D. None of these: This answer is incorrect based on our analysis above.

Considering the explanations given, the correct answer is B. The displacement of O2 from its respiratory pigment occurs more slowly when the pH is alkaline.