A researcher studying a seedling can determine its stage of development according to the molecular phenomena that are occurring.If DNA synthesis is observed,the seedling is at the stage at which

A) gibberellins are secreted by the embryo.
B) the embryonic root,or radicle,begins to grow.
C) imbibition takes place.
D) the endosperm starts metabolizing starches,proteins,and lipids.
E) the aleurone layer assembles enzymes,proteases,and ribonucleases.