The correct option is D Callus
Callus is a mass of unorganized parenchyma cells derived from the plant tissue or explants. In plant biology, callus cells are those cells that cover a plant wound.
Morula is a solid mass of cells resulting from the cleavage of the fertilized egg.
Blastula is a hollow sphere of cells.
Thus, the correct answer is option (A), 'Callus'.