Two coaxial solenoids 1 and 2 of the same length are set so that one is inside the other. The number of turns per unit length are \[{{n}_{1}}\] and \[{{n}_{2}}\]. The currents \[{{i}_{1}}\] and \[{{i}_{2}}\] are flowing in opposite directions. The magnetic field inside the inner coil is zero. This is possible when [Roorkee 2000]

• A.            \[{{i}_{1}}\ne {{i}_{2}}\] and \[{{n}_{1}}={{n}_{2}}\]
• B.            \[{{i}_{1}}={{i}_{2}}\]and \[{{n}_{1}}\ne {{n}_{2}}\]
• C.            \[{{i}_{1}}={{i}_{2}}\] and \[{{n}_{1}}={{n}_{2}}\]
• D.            \[{{i}_{1}}{{n}_{1}}={{i}_{2}}{{n}_{2}}\]