The strongest acid among the following is: o-methoxyphenol, phenol, m-methoxyphenol, p-methoxyphenol

m-Methoxy phenol is the strongest acid. Methoxy group at meta position exerts an only -I effect. Due to this, it withdraws electrons from all the nuclear position of the benzene ring including the one holding the O−H group consequently, electron density in the O−H bond decreases. Hence, m-methoxy phenol becomes more acidic than o and p-methoxy phenols. Option B is correct.