The formula of ethyne is:

The correct option is A

${\mathrm{C}}_2{\mathrm{H}}_2$

The explanation for the correct option:

• Ethyne, also known as acetylene, is an organic chemical compound with the chemical formula C₂H₂.
• Since it is entire chemical composition only features hydrogen and carbon atoms, this compound is a hydrocarbon.
• Ethyne is regarded by many to be the simplest alkyne since it consists of only two carbon atoms, which are triply bonded to each other.
• Pure ethyne is known to be highly unstable.
• Therefore, it is not uncommon for ethyne to be handled in a solution.
• Ethyne (or acetylene) is an unsaturated hydrocarbon since it contains a carbon-carbon triple bond.

The explanation for the incorrect option:

Option B:

• Benzene has the chemical formula ${\mathrm{C}}_6{\mathrm{H}}_6$
• Benzene is the simplest organic and aromatic hydrocarbon.
• It is a naturally occurring substance produced by volcanoes and forest fires.
• Benzene is a closed ring of six carbon atoms linked by bonds that alternate between single bonds and double bonds.

Option C:

• Ethylene is an unsaturated hydrocarbon with the formula${\mathrm{C}}_2{\mathrm{H}}_4$.
• It has one double bond and it is the simplest member of the alkene class of hydrocarbons.
• The structural formula of ethylene ${\mathrm{CH}}_2={\mathrm{CH}}_2$

Option D:

• Ethane is a saturated hydrocarbon found in the gaseous state.
• The formula of ethane is${\mathrm{C}}_2{\mathrm{H}}_6$
• Ethane is synthesized by reduction of ethyl iodide using zinc and copper, it is also synthesized by the Wurtz method.
• It is used in the petrochemical industry as a fraction of that produced in the natural gas liquids plants alone.

Therefore, the correct option is (A) i.e., the formula of ethyne is ${\mathrm{C}}_2{\mathrm{H}}_2$.