The correct option is A Epidermis
A cnidoblast is an explosive cell containing one giant secretory organelle or cnida that defines the phylum Cnidaria. Cnidoblast cells are only found in the epidermis. It is a cell within which nematocyst is developed. In Cnidaria, capsule occurs on the body surface and it is produced by the cnidoblast.
Therefore, the correct answer is option A.