(D) The direction of magnetic field lines inside a bar magnet is from its north pole to its south pole.
This is not true — inside a bar magnet, field lines run from the south pole to the north pole.
The passage states: "Inside the magnet, the direction of field lines is from its south pole to its north pole." Outside the magnet, field lines go from north to south. Examiners expect students to recall this key distinction. Options A, B, and C are all correct properties of a bar magnet.
Source: Chapter 12, Section 12.1 (Magnetic Field and Field Lines)