The is the layer of tissue that forms during gastrulation and becomes the animal's organs. a. ectoderm b. mesoderm c. endoderm

The answer is B. Mesoderm. During gastrulation three layers form. Ectoderm, mesoderm, and endoderm. Mesoderm is the middle layer and from that layer a multitude of tissues and organs develop. The mesoderm develops into connective tissues like cartlage, bone, blood, and blood vessels. The mesoderm can also develop into muscle types like cardiac, skeletal, and smooth.