Answer:The correct options are
A. They begin on north poles and end on south poles.
B. Field lines that are close together indicate a stronger electric field.
Explanation: An area around a magnet where its effect is observed is called magnetic field. Magnetic field is expressed by lines. They move from south pole to the north pole. If the lines are far from each other, it means magnetic field is weak while if the lines are close to each other, it shows that magnetic field is stronger.