​The table below shows different developmental processes and associated signaling molecules/pathways.​

​Which one of the following options represents the correct association of developmental processes and signaling molecules?​

Correct option is A

In developmental biology, axis specification is directed by specific sets of signaling pathways and morphogens. Here's an evaluation of each entry in the table:

A. Dorsal/ventral axis specification in amphibian embryo:

• Correct. This is regulated by Wnt/β-catenin signaling (establishes the dorsal side), BMP4 (ventralizing factor), and Activin/Nodal pathways (involved in mesoderm induction and organizer formation).

B. Dorsal/ventral axis specification in mammalian limb:

• Correct. This involves Engrailed (En1) (ventral ectoderm marker), Wnt7a/β-catenin (dorsal ectoderm), and BMP signaling (influences ventral patterning).

C. Dorsal/ventral axis specification in Drosophila oocyte:

• Incorrect. The correct dorsal-ventral patterning is governed mainly by Toll signaling (leads to Dorsal protein gradient), Spätzle, and Pipe, not FGF, Hh, or Dpp.

D. Anterior/posterior axis specification in mammalian limb:

• Partially correct.Shh (Sonic Hedgehog) from the zone of polarizing activity (ZPA) is key. FGF (from AER) is involved in proximal-distal patterning, not A-P directly. Notch is not a primary player in A-P axis.