A steady current `I` flows along an infinitely long hollow cylindrical conductor of radius `R`. This cylinder is placed coaxially inside an infinite solenoid of radius `2 R`. The solenoid has a `n` turns per unit length and carries a steady current `I`. Consider a point `p` at a distance `r` from the common axis . The correct statement(s) is (are)
A. In the region `0 lt r lt R`, the magnetic field is non - zero
B. In the region `R ltr lt 2R`, the magnetic field is along the common axis
C. In the region `Rlt r lt 2R`, the magnetic field is tangential to the circle of radius `r`, centered on the axis
D. In the region `r gt 2R`, the magnetic field is non - zero