Electrovalent compounds, also known as ionic compounds, are formed by the transfer of electrons from one atom to another. They usually consist of a metal cation and a non-metal anion.

Option 1: Low melting point and low boiling point - This option is incorrect because electrovalent compounds typically have high melting and boiling points. This is due to the strong electrostatic attraction between the oppositely charged ions in the compound.

Option 2: Low melting point and high boiling point - This option is also incorrect. As mentioned before, electrovalent compounds have high melting and boiling points, so this option does not apply.

Option 3: High melting point and low boiling point - This option is incorrect. Electrovalent compounds generally have high melting points, but their boiling points are typically high as well.

Option 4: High melting point and high boiling point - This is the correct answer. Electrovalent compounds have strong ionic bonds that require a large amount of energy to break. This results in high melting and boiling points.

In summary, electrovalent compounds typically have high melting and boiling points due to the strong electrostatic attraction between the ions.