True about sphenoid sinus -

All paranasal sinuses are lined by respiratory epithelium (i.e. ciliated pseudo stratified columnar epithilium) i.e. option a is incorrect. Sphenoid sinus: Important points It is not present at birth It occupies the body of sphenoid Ostrum of sphenoid sinus is situated in the upper part of anterior wall and drains into spheno ethmoidal recess. On x ray: Sphenoid sinus is visible by 4 years of age.