A compound having a bond angle 180° is

The correct option is alkyne.

To understand why an alkyne has a bond angle of 180°, let us look at the hybridization and molecular geometry of different types of hydrocarbons:

1. Alkynes:
Alkynes are characterized by the presence of at least one carbon-carbon triple bond ($C\equiv C$). The carbon atoms involved in the triple bond are sp hybridized. An sp hybridized carbon atom forms two $\sigma$ (sigma) bonds and two $\pi$ (pi) bonds. The two sp hybrid orbitals arrange themselves as far apart as possible to minimize repulsion, which results in a linear geometry. The bond angle in a linear geometry is exactly 180°.

2. Alkanes and Cycloalkanes:
Alkanes and cycloalkanes contain only single bonds. The carbon atoms in these compounds are sp³ hybridized, resulting in a tetrahedral geometry. The typical bond angle for a tetrahedral carbon is approximately 109.5° (though it can vary slightly in cycloalkanes due to ring strain).

3. Alkenes:
Alkenes contain at least one carbon-carbon double bond ($C=C$). The carbon atoms involved in the double bond are sp² hybridized, resulting in a trigonal planar geometry with a typical bond angle of approximately 120°.

Therefore, the hydrocarbon family that has a characteristic bond angle of 180° is the alkyne family.