In Many Animal Embryos,the Eye Is the First Organ to Develop.The

In many animal embryos,the eye is the first organ to develop.The Pax6 protein is important to eye development;its absence may prevent the formation of eyes in mice and humans.Pax6 probably acts as a(n)

A) structural protein in cells of the retina.
B) intercellular signal between retinal and lens cells.
C) transcriptional factor for photoreceptors.
D) extracellular matrix protein secreted by the retina.