Which Statements About the Adaptive Radiation of New Zealand Alpine

Which statements about the adaptive radiation of New Zealand alpine buttercups are true? Check all that apply.

A) Allopatric speciation occurred mainly during periods of glacial recession.
B) Divergence occurred mainly during periods of glacial advance.
C) The availability of a variety of habitats favored diversification.
D) Reproductive isolation was reinforced mainly during periods of glacial recession.