Answer:
A. When the current is shut off, the magnetic field disappears.
Step-by-step explanation:
Electromagnetism is a method in which magnetism is obtained from an electric current. It is an artificial way of producing a strong magnetic fields due to the flow of current.
Since the magnetic effect observed is due to the flow of an electric current, so when the current is shut off, the magnetic field disappears.
It has a wide range of applications in manufacturing industries, electric bells, induction coil etc.