Assertion (A): In human beings, the respiratory pigment is haemoglobin present in red blood cells. Reason (R): Haemoglobin has a very high affinity for carbon dioxide.

The chapter states: 'In human beings, the respiratory pigment is haemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles.' So the Assertion (A) is true — haemoglobin, the respiratory pigment, is indeed present in the red blood corpuscles.

However, the Reason (R) is false, because haemoglobin has a high affinity for oxygen, not carbon dioxide. In fact, the chapter clarifies that 'carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved form in our blood' — meaning $\text{CO}_2$ transport largely bypasses haemoglobin and instead occurs dissolved in plasma.

Since A is true but R is false, the correct option is (C).

(A) and (B) are incorrect because they treat R as true, which it is not.

(D) is incorrect because it treats A as false, but A is actually true.