Two coaxial solenoids 1 and 2 of the same length are set so that one is inside the other. The nu...

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
(A) \( I_{1} \neq I_{2} \) and \( n_{1}=n_{2} \)
(B) \( I_{1}=I_{2} \) and \( n_{1} \neq n_{2} \)
(C) \( I_{1}=I_{2} \) and \( n_{1}=n_{2} \)
(D) \( I_{1} n_{1}=I_{2} n_{2} \)