According to the theory of island biogeography which of the following ecosystems is not an island ecosystem? a. cave b. salt marsh c. mountaintop d. desert oasis

This the theory which was introduced just to find out more about the richness of the different islands.

But according to the question, the desert oasis does not form an island ecosystem and therefore it should be ruled out from all the options that are given above.

I think salt marsh is the answer