Question

multiple choice question
ectoderm, endoderm, and mesoderm are the three primary
germ layers in many animal embryos.
types of body cavities found in animals.
types of mollusks.
classes of extinct fishes.

Explanation:

Ectoderm, endoderm, and mesoderm are fundamental structures in animal embryonic development. They are known as germ layers. Body cavities (like coelom, pseudocoelom) are different concepts. Mollusks are a phylum with specific characteristics. Extinct fishes are a different taxonomic and evolutionary category.

Answer:

germ layers in many animal embryos.