What Does the ABC Model of Flower Development Attempt to Explain

What does the ABC model of flower development attempt to explain?

A) how different combinations of gene products trigger the formation of different floral organs
B) why petals are found on the inside of the whorl of sepals instead of on the outside
C) why the four types of floral organs occur in whorls
D) why apical meristems are converted to floral meristems in response to specific cell-to-cell signals