Consider the following reaction ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}\left(\mathrm{A}\right)+{\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{B}\right)\stackrel{{\mathrm{H}}^{+}}{\to }{\mathrm{CH}}_3{\mathrm{COOCH}}_2{\mathrm{CH}}_3 + \mathrm{HOH}$

In the above reaction, ester formation takes place by

Breaking of O – H bond of (A) and C – O bond of (B)

Breaking of C – O bond of (A) and C – O bond of (B) 

Breaking of C – O bond of (A) and O – H bond of (B) 

Breaking of O – H bond of (A) and O – H bond of (B)