One of the ex-situ conservation methods for endangered species is:

Options

A. Wildlife sanctuaries
B. Biosphere Reserves
C. Cryopreservation
D. National Parks

Answer

To solve the question regarding ex-situ conservation methods for endangered species, we will analyze each option provided and identify the correct one.

### Step-by-Step Solution:

1. **Understand Ex-situ Conservation**: Ex-situ conservation refers to the preservation of species outside their natural habitats. This can include methods such as breeding in captivity, botanical gardens, zoos, and cryopreservation.

2. **Evaluate the First Option - Wildlife Sanctuary**:
- Wildlife sanctuaries are areas where wild animals are protected in their natural environment.
- Since this method involves conserving species in their natural habitat, it is classified as in-situ conservation.
- **Conclusion**: This option is incorrect.

3. **Evaluate the Second Option - Biosphere Reserve**:
- Biosphere reserves are designated areas that conserve biodiversity and promote research and education.
- Similar to wildlife sanctuaries, biosphere reserves protect species in their natural habitats, making this an in-situ conservation method.
- **Conclusion**: This option is incorrect.

4. **Evaluate the Third Option - Cryopreservation**:
- Cryopreservation is a technique used to preserve cells, tissues, or any biological constructs by cooling them to very low temperatures.
- This method allows for the long-term storage of genetic material and is conducted outside the natural habitat, making it an ex-situ conservation method.
- **Conclusion**: This option is correct.

5. **Evaluate the Fourth Option - National Park**:
- National parks are protected areas that conserve wildlife and natural resources in their natural settings.
- Like wildlife sanctuaries and biosphere reserves, national parks are examples of in-situ conservation.
- **Conclusion**: This option is incorrect.

6. **Final Conclusion**:
- After evaluating all the options, the only method that qualifies as an ex-situ conservation method for endangered species is **cryopreservation**.

### Final Answer:
The correct answer is **cryopreservation**.