Which of the following communities would be considered to have the greatest species richness?

A) an elk gut with 240 species of microorganisms, where 95 percent of the microorganisms are bacteria
B) a small forest in North America made up of 10 species of birds, 125 insect species, and five tree species
C) a community of 150 small invertebrates classified as 15 different species living within a puddle
D) a large grassland community in South America with 175 species of grasses, birds, and insects