What characteristic defines a protic solvent?

A protic solvent is characterized by the presence of protons (hydrogen atoms) that are directly bonded to electronegative atoms, typically oxygen or nitrogen. This means that in a protic solvent, you'll find functional groups such as -OH (hydroxyl) or -NH (amines), which allow for the formation of hydrogen bonds due to their ability to donate protons. These solvents are effective in solvating ions and polar molecules, as well as participating in acid-base reactions.

This definition directly aligns with the chosen answer, which highlights the presence of protons directly bonded to electrophilic compounds. This ability to donate protons is what distinguishes protic solvents from aprotic solvents, which lack such protons and cannot participate in hydrogen bonding.

In contrast, options mentioning only non-polar or only polar components do not accurately address the unique feature of protic solvents. Non-polar components do not interact favorably with ions or polar solutes in the same way that protic solvents do, while the reference to only polar components fails to capture the essential presence of hydrogen-bonding protons that defines protic solvents. Thus, the correct answer emphasizes the significance of protons in these solvents.