How does a magnetic compass needle behave in a magnetic field ?
A. It assures a position right angle to magnetic field
B. It assures a position which follows a line of magnetic field
C. It start rotating
D. none of these

Hint: Magnetic compass is used for navigation and to show direction. Magnetic compass has a rod and this rod is made of lodestone (a magnetized ore of iron it is a natural form). We sometimes call this rod needle of compass which shows directions.

Complete step by step solution:
We know earth behaves like a bar magnet which has its own magnetic field .The needle of magnetic compass indicates the direction of magnetic north at the point of earth surface. Geomagnetic field is an alternative name of earth magnetic field. This magnetic field extends to the infinity. The magnetic line of force of earth emerges from the north pole and ends up to the south pole and it makes a loop just like in a bar magnet the magnetic line of force emerges from north and enters to the south pole. So the needle has the tendency to align itself to the magnetic line of force. Here the option that assures a position which follows a line of magnetic field is the correct.

Note: In this problem we have used the approach of a bar magnet as we know about the direction of the bar magnet and it’s behaviour when it comes in contact with the magnetic compass. The line of magnetic field makes a close loop but it starts from north pole to south pole and magnetic needle follows its direction as it is made of iron or steel and magnetized by lodestone. So when we place it in a magnetic field it assures a position which follows a line of magnetic field.