The correct answer is d) ionic bonds.
Ionic bonds occur when one atom donates an electron to another atom, resulting in the formation of positively and negatively charged ions. These oppositely charged ions experience an electrostatic attraction, which holds them together in a compound. For example, in sodium chloride (table salt), sodium (Na) loses one electron to become a Na+ ion, while chlorine (Cl) gains that electron to become a Cl– ion. The resulting ionic bond between Na+ and Cl– creates a stable compound.