Assertion : We cannot think of magnetic field configuration with three poles. Reason : A bar magnet does exert a torque on itself due to its own field.

Step-by-step solution

It is quite clear that magnetic poles always exists in pairs. Since, one can imagine magnetic field configuration with three poles. When north poles or south poles of two mangets are glued together. They provide a three pole field configuration. It is also know that a bar magnet does not exert a torque on itself due to its own field.