The correct answer here is D - Why. Whilst some of the other possible
answers here might need help from other scientists, in that to
understand when there may need to be dating methods from a scientist, or
to understand where the aid of a geologist might be needed, it is only
the why that might require help from other social scientists. For
example, anthropologists, sociologists and psychologists might be able
to help explain why a society was a certain way.
