The formation of the lens from the ectoderm layer during frog embryonic development is dependent upon signals received from the underlying optic vessicle. This is an example of:

A.	embryonic induction The optic vessicle induces the ectoderm layer above it to become placode tissue. The placode tissue then induces the formation of the optic cup, which in turn induces the placode tissue to form the cornea and lens of the eye.
B.	pattern formation
C.	homeotic gene regulation
D.	polarity in the embryo
E.	apical dominance