What functional group is characteristic of alkynes?

The functional group that is characteristic of alkynes is the C≡C triple bond. Alkynes are hydrocarbons that contain at least one triple bond between carbon atoms, which distinguishes them from other types of hydrocarbons such as alkenes, which have double bonds, and alkanes, which consist solely of single bonds. The presence of the triple bond in alkynes not only affects their chemical reactivity but also contributes to their unique physical properties.

The C-H bond exists in alkynes, like in many other organic compounds, but it is not exclusive or defining for alkynes. The defining feature really is the presence of the triple bond, making it clear that the correct answer emphasizes the unique characteristic that sets alkynes apart from alkenes and alkanes.