Rhinolith can cause perforation of nasal septum by-

Ans. is 'a' i.e., Pressure necrosis * A rhinolith usually forms around the nucleus of a small exogenous foreign body, blood clot or inspissated secretions by slow deposition of calcium and magnesium salts.* Over a period of time, it grows into a large, irregular mass, which fills the nasal cavity and then may cause pressure necrosis of the septum and/or lateral wall of nose.