For a current in a long straight solenoid,$N-$ and $S-$ poles are created at the two ends. Among the following statements,the incorrect statement is:

• A
  The field lines inside the solenoid are in the form of straight lines,which indicates that the magnetic field is the same at all points inside the solenoid.
• B
  The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron,when placed inside the coil.
• C
  The $N-$ and $S-$ poles exchange positions when the direction of current through the solenoid is reversed.
• D
  The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.