What is the pattern of magnetic fields inside the solenoid?

(A) Radial.
(B) Uniform.
(C) Both (A) and (B).
(D) Circular.

Hint In this question, we will use the concept of the solenoid that is a solenoid containing the large number field lines that are parallel in nature. Therefore, the magnetic field at all the points inside the solenoid will not change.

Complete step by step answer
We can define the solenoid as a type of the electromagnet, which is used to generate the controlled magnetic field through a strongly packed helix or a coil. So the solenoid is a coil which is having greater length from its diameter.
To understand the given information, let us draw the diagram of the magnetic field lines of the solenoid which is carrying a current
 

 From the above figure, we can see that the field lines are in the form of parallel lines inside the solenoid and the direction of the magnetic field lines are from south to north pole inside the solenoid coil. The magnetic field lines never intersect to each other.
From the above information, we can say that the magnetic field inside solenoid at all points is the same or the magnetic field inside the solenoid is uniform.

Therefore, we can say that the magnetic field inside the solenoid at all points is the same or uniform. So, the option (B) is correct.

Note
As we know that a solenoid is a long coil of the large number of the insulated wires. The magnetic field pattern produced inside a Solenoid is similar to the magnetic field produced by a bar magnet.