a
\((a)\) Cyclic hydrocarbon in which all the carbon atoms are present in the same plane is benzene. In this \(C - C\) bond length is \(1.39\,\mathop A\limits^o \) which is more than \(1.34\,\mathop A\limits^o \) but less than \(1.54\,\mathop A\limits^o \). Hence bond angle is \({120^o}\) with \(s{p^2}\) hybridization.