Correct option is A
Explanation-
Epiboly is the movement during embryonic development where an epithelial sheet spreads as a unit to enclose deeper layers. This process involves the thinning and spreading of a cell sheet (usually ectodermal cells) to cover the entire embryo. It is commonly observed during gastrulation in amphibians and other vertebrates.
Incorrect options:
Option b - Emboly – Not a standard term in developmental biology; might be a distractor.
Option c - Involution – Involves the inward rolling of a sheet of cells, but not spreading over deeper layers.
Option d - Ingression – Refers to individual cells migrating inward, not the movement of a sheet as a unit.
Final Answer: Option a – Epiboly
