Ans. is 'a' i.e., Opening of nasolacrimal ductLateral wall of nose It has 3 bony projections called as turbinates or conchae. From below upwards they are inferior, middle and superior turbinates. The inferior turbinate is a separate bone, while rest of the turbinates are a pa of ethmoidal bone. Below and lateral to each turbinate is the corresponding meatus. Inferior turbinate is largest one. 1. Inferior meatusIt is the largest meatus. It's highest point is the junction of anterior and middle 1 /3rd. Nasolacrimal duct opens in the inferior meatus, just anterior to its highest point (it is closed by a mucosal flap called Hasner's valve). 2. Middle meatusIt lies below the middle turbinate (middle concha), i.e. between middle turbinate and inferior turbinate. The impoant structures in middle meatus are :-Hiatus semilunarisEthmoidal infundibulum :- Frontal sinus, maxillary sinus and the anterior ethmoidal sinuses drain into it.Anterior /Posterior fontanelle :- Accessory ostia are found mostly in the posterior fontanelle.Uncinate process :- It paly covers the opening of maxillary sinus.Bulla ethmoidalis :- Middle ethmoidal sinuses open on or above it.Atrium is a shallow depression in front of the middle turbinate. Agger nasi is an elevation just anterior to the attachement of middle turbinate. 3. Superior meatusIt lies below the superior turbinate and posterior ethmoidal sinuses open into it. 4. Spheno-ethmoidal recessIt lies above the superior turbinate and receives the opening of sphenoid sinus.