Cribriform plate forms-

Ans. is 'a' i.e., Roof of olfactory region Internal noseo Internal nose has following partsNasal cavity proper Internal nose is divided into right and left nasal cavities by nasal septum. Each nasal cavity communicates with the exterior through naris or nostrils and with nasopharynx through posterior nasal aperture or posterior nares or choana.I'Cstibule of nose Anterior and inferior part of the nasal cavity is lined by skin and is called vestibule of nose. It contains sebaceous glands, hair follicles and the hair called vibrissae.o Each nasal cavity has a lateral wall, a medial wall (nasal septum ), a roof, and a floor.o The olfactory' mucosa lines upper 1/3 of nasal cavity including the roof formed by cribriform plate, and medial and lateral wall up to the level of superior eoncha.