When the Major Axes of the Fruit-Fly Embryo Have Been $\rightarrow$

When the major axes of the fruit-fly embryo have been established, segmentation genes determine the number, orientation, and basic organization of the body segments.
-The correct sequence in which the segmentation genes act is:

A) segment-polarity genes $\rightarrow$ gap genes $\rightarrow$ pair-rule genes.
B) gap genes $\rightarrow$ pair-rule genes $\rightarrow$ segment-polarity genes.
C) segment-polarity genes $\rightarrow$ pair-rule genes $\rightarrow$ gap genes.
D) gap genes $\rightarrow$ segment-polarity genes $\rightarrow$ pair-rule genes.