The Simplified Drawing Below Depicts Early Stages of Animal Development

Short Answer

The simplified drawing below depicts early stages of animal development. Indicate which letter (A to E) in the drawing corresponds to each of the following terms. Your answer would be a five-letter string composed of letters A to E only, e.g. ECDBA.

( ) Blastula
( ) Ectoderm
( ) Endoderm
( ) Mesoderm
( ) Gastrula