At the cephalic end of primitive streak, closely packed cells form a loci thickening known as:

Explanation

Explanation:At the cephalic end of the primitive streak, closely packed cells form a locai thickening known as Hensen's node. It is the site where the gastrulation begins and the 3 germ layers are first formed.This option is not correct. The primitive ridge is a thickened area of the ectoderm that lies above the notochord in the developing embryo. It is formed during neurulation and serves as a signaling center that regulates the patterning of the neural tube.This option is also incorrect. The gastrocoel is a cavity that forms in the developing embryo as the gut tube forms by folding the endodermal layer. It eventually becomes the lumen of the developing digestive tract.This option is also incorrect. The primitive gut is the initial tube-like structure that develops from the endoderm during gastrulation. It later gives rise to the digestive tract and associated organs.