Biodiversity includes the diversity within species (genetic diversity), ecosystems (ecosystem diversity), and between species (species diversity). The examples in the question have three options of diversity within species and one that is between species. Therefore, considering the alternatives and the definition of the types of biodiversity and what is the species diversity, the letter D (bears, skunks, and woodpeckers living in a forest) is the correct, since in it we have representatives of three different species that share the same space.