Which statement is true about an ideal solenoid?
A. The internal magnetic field is approximately uniform while the external field is weak.
B. The magnetic field is approximately uniform and roughly equal strength both inside and outside the solenoid.
C. The internal magnetic field strength cannot be calculated using Ampere's law.
D. The internal magnetic field is weak while the external field is approximately uniform.
E. The internal magnetic field is inversely proportional to the radius of the coils in the solenoid.