Rate of change of torque \[\tau \] with deflection\[\theta \]is maximum for a magnet suspended freely in a uniform magnetic field of induction B, when [MP PET 1994]

• A.            \[\theta =0{}^\circ \]        
• B.            \[\theta =45{}^\circ \]
• C.            \[\theta =60{}^\circ \]      
• D.            \[\theta =90{}^\circ \]