Which of the Following Best Explains Why the Rock Chimneys

Which of the following best explains why the rock chimneys of the Lost City host such a variety of unique microbial communities?

A) The height of the chimneys creates a gradient of temperatures (hottest at the top and coolest at the bottom) along the chimney; these, in turn, become separate environments and host different communities.
B) The height of the chimneys creates a gradient of pH (most acidic at the top and most basic at the bottom) along the chimney; these, in turn, become separate environments and host different communities.
C) Although temperatures, pH, and other factors are the same all over each chimney, the chimneys are so big that different communities can occupy different sections of the chimney.
D) The Lost City comprises a huge number of rock chimneys, each of which has its own unique environment; this means that each chimney hosts its own unique microbial community.
E) None of the above.