* Ionic Bonds: Ammonium chloride is formed by the electrostatic attraction between the positively charged ammonium ion (NH₄⁺) and the negatively charged chloride ion (Cl⁻). This is the defining characteristic of an ionic bond.

* Covalent Bonds: Within the ammonium ion (NH₄⁺), the nitrogen atom is bonded to four hydrogen atoms through shared electron pairs. This sharing of electrons is the basis of a covalent bond.

Let's look at the other options:

* A) Ammonia (NH₃): Ammonia contains only covalent bonds between nitrogen and hydrogen atoms.

* C) Hydrogen chloride (HCl): Hydrogen chloride contains a single covalent bond between hydrogen and chlorine.

* D) Sodium chloride (NaCl): Sodium chloride is a classic example of an ionic compound with only ionic bonds between sodium and chlorine.

In summary: Ammonium chloride (NH₄Cl) is the only compound that exhibits both ionic bonds (between NH₄⁺ and Cl⁻) and covalent bonds (within the NH₄⁺ ion).