Final answer:
A hydrogen bond must include a hydrogen atom that is covalently bonded to a highly electronegative atom such as fluorine, oxygen, or nitrogen, and is attracted to another electronegative atom.
Step-by-step explanation:
The type of bond that must include a hydrogen molecule is known as a hydrogen bond. Hydrogen bonding is a type of intermolecular force where a weakly positive hydrogen atom, which is already covalently bonded to an electronegative atom such as fluorine, oxygen, or nitrogen, is attracted to another electronegative atom (usually from a different molecule). Polar molecules, like water, extensively form hydrogen bonds, which give water its unique properties and are also crucial in biological systems, such as maintaining the structure of DNA and proteins.