Medulla oblongata develops from
(a) Ectoderm
(b) Endoderm
(c) Mesoderm
(d) Mesenchyme

Hint: The outermost layer of cells among the three primary layers of the embryo. It is formed during the early developmental stages, or the parts derived from this, which include the epidermis, nerve tissue, nephridia, lining of mouth, anus, nostrils, sweat glands, hair, and nails.

Complete answer:
The medulla oblongata develops from the ectoderm. It is the lowest part of the brain and the lowest portion of the brainstem (part of the brain) . The medulla oblongata is connected by the pons (bridge- like structure and part of the brainstem) to the midbrain and is continuous posteriorly with the spinal cord, with which it merges at the gap (foramen magnum) at the bottom of the skull.
The medulla oblongata plays an important role in the transmission of signals between the spinal cord and the higher parts of the brain and in controlling autonomic activities, such as the heartbeat and external respiration process.
Once an embryo is formed with three established germ layers (endoderm, mesoderm, and ectoderm) , differentiation among these three layers begins. Within the ectoderm, the process of neurulation begins, which results in the formation of the neural tube, neural crest cells, and the epidermis. The neural tube cells give rise to the central nervous system, neural crest cells, peripheral and enteric nervous system. This Medulla oblongata is the part of the central nervous system.

Additional Information:
- The word ectoderm is derived from the Greek word ‘ektos’ meaning "outside", and ‘derma’ meaning skin.
- Heinz Christian Pander, a German–Russian biologist, discovered the three germ layers.
So, the correct answer is, ‘Ectoderm.’

Note: The medulla or medulla oblongata develops from the secondary brain vesicle (one of the 5 vesicles during embryo development) called the myelencephalon. The myelencephalon, in turn, is formed from the earlier primary brain vesicle, rhombencephalon, which in turn is formed from the neural tube, hence, ectodermal in origin.