the myelencephalon is composed largely of\n\nganglia.\n\nventricles.\n\ntracts.\n\ncolliculi.

Brief Explanations:

The myelencephalon, part of the hind - brain, is mainly composed of tracts. Tracts are bundles of nerve fibers. Ganglia are clusters of nerve cell bodies outside the central nervous system. Ventricles are fluid - filled cavities in the brain. Colliculi are structures in the mid - brain.

Answer:

C. tracts