Which of the following statements is incorrect regarding magnetic field lines?<b>(a) </b>The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points<b>(b)</b>Magnetic field lines are closed curves<b>(c)</b>If magnetic field lines are parallel and equidistant, they represent zero field strength<b>(d)</b>Relative strength of magnetic field is shown by the degree of closeness of the field lines