When the Bicoid protein is expressed in Drosophila, divisions between cells in the embryo are not yet fully developed. This information helps to explain which observation by Nüsslein-Volhard and Wieschaus?
(A) mRNA from the egg is translated into the Bicoid protein. (B) Bicoid protein diffuses throughout the embryo in a concentration gradient.
(C) Bicoid protein serves as a transcription regulator. (D) Bicoid protein determines the dorso-ventral axis of the embryo.