Answer:
The magnetic field remains the same.
Explanation:
If a solenoid has length L, N windings, and radius b, then the magnetic field inside the solenoid is given by :
[tex]B=\mu_o NI[/tex]
[tex]\mu_o[/tex] is magnetic permeability
If the radius of the solenoid were doubled and all other quantities remained the same, the magnetic field inside the solenoid would remains the same as it is independent of the radius of the solenoid.