(a) Ferromagnet
Explanation:
Ferromagnetism is defined as the property by which certain magnets form the permanent magnets.
It is tone of the strong magnetism and it is common phenomenon of magnet in the everyday life of magnetism.
Permanent magnets are made up of ferromagnetic material, in this if the magnetic field is applied then this material is magnetized but do not losses its magnetic property after removal of external magnetic field.
As the clump of colored fluid at the bottom of the lava lamp reaches the top, which has increased?
Its Density is the answer
Explanation: