Answer:
B. In an area where a glacier has retreated
Explanation:
Primary succession, starts at a lifeless area where it has been affected by lava flood and/or retreated glacier therefore the answer is B.
Studies of populations that reveal correlations between dietary habits and disease incidence are epidemiological studies.
Sorry for a late answer... But here we go!
https://www.sciencelearn.org.nz/resources/102-methods-of-pollination