Blood platelets are present in the blood of
(a) Birds
(b) Reptiles
(c) Mammals
(d) Amphibians

Options

A. Birds
B. Reptiles
C. Mammals
D. Amphibians

Answer

To determine which group of animals has blood platelets, we can analyze the options provided:

1. **Understanding Blood Components**:
- Blood consists of various components, primarily red blood cells (RBCs), white blood cells (WBCs), and platelets (also known as thrombocytes).
- Platelets are crucial for blood clotting and are produced from large cells in the bone marrow called megakaryocytes.

2. **Analyzing Each Option**:
- **(a) Birds**: Birds do have nucleated red blood cells, but they do not have platelets in the same form as mammals. Instead, they have thrombocytes, which are functionally similar but structurally different.
- **(b) Reptiles**: Similar to birds, reptiles also possess nucleated red blood cells and thrombocytes instead of platelets.
- **(c) Mammals**: Mammals are known to have true platelets that are involved in blood clotting. These platelets are formed from the fragmentation of megakaryocytes.
- **(d) Amphibians**: Amphibians have nucleated red blood cells and also possess thrombocytes, not true platelets.

3. **Conclusion**:
- Based on the analysis, blood platelets are specifically present in mammals. Therefore, the correct answer is **(c) Mammals**.

### Final Answer:
The correct option is **(c) Mammals**.