Explanation

Ethyne (acetylene, HC≡CH) contains two carbon atoms joined by a triple bond — one sigma bond and two pi bonds — with each carbon also bonded to one hydrogen by a single bond. A single bond would give ethane and a double bond would give ethene, so options A and B are wrong, and there is no carbon–hydrogen double bond (option D). The carbon–carbon triple bond is the defining feature of alkynes such as ethyne.