One of the ex-situ conservation methods for endangered species isA Wildlife sanctuaries B Biosphere reserves C Tissue culture D National parks

The ex-situ conservation methods refer to the techniques for conservation of biodiversity and genetic resources outside their natural habitats. These methods are usually used when in-situ conservation methods, or conservation in the natural habitats, are not effective.

Here are the options you provided explained:

A. Wildlife sanctuaries: These are in-situ conservation methods. They are areas where wildlife is protected and preserved in their natural environments.

B. Biosphere reserves: These are also in-situ conservation methods. They are areas set aside for the conservation of the biodiversity and the culture of that area.

C. Tissue culture: This is an ex-situ conservation method. It is a technique where cells, tissues or organs are grown in an artificial medium separate from the parent organism. This is often used in plants.

D. National parks: These are in-situ conservation methods. They are areas set aside by the government for the preservation of wildlife and their habitats.

So, the correct answer to your question is C. Tissue culture. This is an ex-situ conservation method used for endangered species.