Explanation:

- Magnetization:

- This phenomenon occurs when a material is subjected to a magnetic field, not an electric field. It results in the alignment of magnetic moments in the material.

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- Polarization:

- Correct Answer

- When a dielectric material is placed in an electric field, its molecules align with the field, creating a dipole moment. This is known as polarization.

- Photoionization:

- This process involves the ionization of atoms or molecules through the absorption of light (photons). It is unrelated to electric fields affecting dielectrics.

- Circularization:

- This term is not commonly associated with dielectrics in electric fields. It typically refers to making something circular or having a circular pathway.

In summary, Polarization is the correct phenomenon realized when a dielectric is in an electric field.