Which of the following best describes the magnetic field lines around an isolated, permanent bar magnet?

A. The field lines go from the magnet's south pole into its north pole.
B. The field points out along radial lines from the bar magnet, extending straight out to infinity.
C. The field lines go from the magnet's north pole into its south pole.
D. The field points straight into the bar magnet along radial lines that extend to infinity.