**Core Concept**
Covalent bonds are a type of chemical bond where two or more atoms share one or more pairs of electrons to achieve a stable electronic configuration. This sharing of electrons leads to a strong and stable attraction between the atoms, resulting in the formation of a molecule.

**Why the Correct Answer is Right**
The correct answer is related to the definition of covalent bonds. Covalent bonds are characterized by the sharing of electron pairs between atoms, which leads to the formation of a molecule. This is in contrast to ionic bonds, where electrons are transferred from one atom to another.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the nature of covalent bonds. While it is true that covalent bonds involve the sharing of electrons, the statement is too vague and does not provide a clear definition.

**Option B:** This option is incorrect because it describes a characteristic of ionic bonds, not covalent bonds. Ionic bonds involve the transfer of electrons, not sharing.

**Option C:** This option is incorrect because it describes a characteristic of hydrogen bonds, not covalent bonds. Hydrogen bonds are a type of intermolecular force that arises between molecules with a hydrogen atom bonded to a highly electronegative atom.

**Clinical Pearl / High-Yield Fact**
A key characteristic of covalent bonds is that they are typically strong and stable, resulting in the formation of molecules with fixed shapes and properties. This is in contrast to ionic bonds, which are often weaker and more labile.

**Correct Answer: D. Covalent bonds involve the sharing of electron pairs between atoms.**