Q. The fluid-filled cavity in a blastula is calle

Explanation by: Mr. Dubey

The blastocoel is the fluid-filled cavity that forms inside the blastula during early embryonic development. It provides space for cell movement and plays a crucial role in gastrulation, the process that leads to the formation of different germ layers.
(A) Coelom → The body cavity formed later in development, lined by mesoderm.
(C) Neurocoel → The cavity within the neural tube, which later forms the brain and spinal cord.
(D) Gastrocoel → The primitive gut cavity formed during gastrulation, also called archenteron.
Thus, the correct answer is (B) Blastocoel.