Step 1: +M Effect of \( \text{-OH} \).
The hydroxyl group (-OH) is an electron-donating group via resonance (the +M effect). This increases the electron density at the \( \alpha- \) and \( \beta- \) positions of the aromatic ring, making electrophilic substitution easier.
Step 2: Conclusion.
The correct answer is (A), \( \text{-OH} \) group exhibits +M effect.