# The reaction $R-Cl+R'ONa$---------->$ROR'+Nacl$.The reaction is catalysed by the addition of small amounts of $NaI$ because

(a) Iodide ion is better nucleophile than OR ion

(b) Iodide ion is better leaving group than chloride ion

(c) Iodide ion is both better nucleophile as well as good leaving group

(d) Iodide ion can increase the leaving tendency of chloride ion with its greater polarisablity

electro negativity of halogens is in the order F > Cl > Br > I.
Iodide ion is least electronegative and a good nucleophile and also a very good leaving group