Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): The red colour of blood is due to haemoglobin. Reason (R): Haemoglobin is a red coloured pigment.

Introduction / Context:
This is a basic human physiology question about blood composition. It connects the colour of blood with the presence of haemoglobin in red blood cells. Assertion–reason format is used to ensure that students know not only the fact but also the reason behind the colour.

Given Data / Assumptions:

• Assertion (A): The red colour of blood is due to haemoglobin.
• Reason (R): Haemoglobin is a red coloured pigment.
• We assume standard school level biology content on blood and haemoglobin.
• The question asks whether both statements are true and whether R explains A.

Concept / Approach:
Blood contains red blood cells whose cytoplasm is rich in haemoglobin, a protein that binds oxygen. Haemoglobin contains iron and gives red blood cells their distinctive colour. Large numbers of these red cells suspended in plasma give whole blood its red appearance. Therefore, the pigment nature of haemoglobin is directly responsible for blood colour.

Step-by-Step Solution:
Step 1: Evaluate Assertion (A). It is commonly taught that blood is red because of haemoglobin in red blood cells. Haemoglobin is the main coloured component influencing blood colour. So A is true.Step 2: Evaluate Reason (R). Haemoglobin is indeed a coloured protein. In its oxygenated form it is bright red; in deoxygenated form it is darker. Thus describing it as a red pigment is acceptable in school biology. So R is also true.Step 3: Check whether R explains A. Blood appears red because millions of haemoglobin containing red blood cells are present in it. Since haemoglobin itself is a red pigment, its presence is exactly the reason why the overall colour of blood is red.Step 4: Therefore both A and R are true, and R is the correct explanation of A.

Verification / Alternative check:
If there were no haemoglobin or if it were not a red pigment, blood would not appear red in the same way. For example, organisms with different respiratory pigments have differently coloured blood. This shows that the pigment determines colour, confirming the explanatory relationship between haemoglobin being a red pigment and blood colour.

Why Other Options Are Wrong:
Option b suggests that R does not explain A even though the pigment property is exactly what gives blood its colour. Option c and option d claim that either the assertion or the reason is false, which would contradict well established biology about the role and characteristics of haemoglobin.

Common Pitfalls:
Some students may think that plasma colour or other components dominate, but plasma alone is pale straw coloured and would not give the deep red seen in whole blood. Remember that it is the red blood cells packed with haemoglobin that are mainly responsible for colour.

Final Answer:
The correct option is that both Assertion (A) and Reason (R) are true and R is the correct explanation of A.