Classification Of Hydrocarbons

Unsaturated hydrocarbons are those that contain one or more double or triple bonds between carbon atoms. These compounds do not have the maximum possible number of hydrogen atoms.
Butane (C₄H₁₀) is a saturated hydrocarbon with only single bonds between carbon atoms.
Butyne (C₄H₆) is an unsaturated hydrocarbon as it contains a triple bond between carbon atoms.
Isobutane (C₄H₁₀) is a saturated hydrocarbon, similar to butane.
Cyclobutane (C₄H₈) is a saturated hydrocarbon, despite having a ring structure, as all carbon-carbon bonds are single bonds.
Thus, the correct answer is Butyne, which is an unsaturated hydrocarbon due to the presence of a triple bond.

The correct option is (B): Butyne