Two bar magnets with magnetic moments 2 M and M are fastened together at right angles to each other at their centres to form a crossed system, which can rotate freely about a vertical axis through the centre. The crossed system sets in earth?s magnetic field with magnet having magnetic moment 2M making and angle q with the magnetic meridian such that [AFMC 1999]

• A.            \[\theta ={{\tan }^{-1}}\left( \frac{1}{\sqrt{3}} \right)\]     
• B.            \[\theta ={{\tan }^{-1}}\left( \sqrt{3} \right)\]
• C.            \[\theta ={{\tan }^{-1}}\left( \frac{1}{2} \right)\]     
• D.            \[\theta ={{\tan }^{-1}}\left( \frac{3}{4} \right)\]