Which one is the most reactive towards an electrophilic reagent?
Key Idea Electron withdrawing substituent deactivates the benzene nucleus towards electrophilic substitution while electron releasing substituent activates the ring towards electrophilic substitution.
Among the given, - OH has the higher electron donating tendency and thus, activates the ring more towards electrophilic substitution.
Hence,
It is more reactive towards electrophilic reagent.