Which of the following components are not present in RBC of mammals?
(i) Nucleus
(ii) Mitochondria
(iii) Plasma membrane
(iv) Ribosomes

Options

A. (i), (ii)
B. (i), (ii), (iii)
C. (i), (ii), (iv)
D. (i), (iv)

Answer

To answer the question "Which of the following components are not present in RBC of mammals?" we will analyze each option provided:

1. **Nucleus**:
- Mature red blood cells (RBCs) in mammals are unique because they do not contain a nucleus. During their maturation process, RBCs lose their nucleus to make more space for hemoglobin, which is essential for oxygen transport. Therefore, the nucleus is **not present** in mature mammalian RBCs.

2. **Mitochondria**:
- Similar to the nucleus, mature RBCs also lack mitochondria. The absence of mitochondria is due to the fact that RBCs rely on anaerobic metabolism for energy, allowing them to efficiently transport oxygen without using it. Thus, mitochondria are **not present** in mature mammalian RBCs.

3. **Plasma membrane**:
- The plasma membrane is a crucial component of all cells, including RBCs. It is a lipid bilayer that surrounds the cell and regulates the movement of substances in and out of the cell. Therefore, the plasma membrane is **present** in mammalian RBCs.

4. **Ribosomes**:
- Ribosomes are responsible for protein synthesis. In mature RBCs, there is no need for protein synthesis as they do not have a nucleus to provide instructions for making proteins. Consequently, mature RBCs do not contain ribosomes. Thus, ribosomes are **not present** in mature mammalian RBCs.

### Conclusion:
Based on the analysis:
- The components **not present** in the RBCs of mammals are:
- (i) Nucleus
- (ii) Mitochondria
- (iv) Ribosomes

The correct answer is: **(i), (ii), and (iv)**.