$\begin{array}{1 1}(a)\;\text{the molecular plane}\\(b)\; \text{a plane parallel to the molecular plane}\\(c)\;\text{a plane perpendicular to the molecular plane which bisects the carbon-carbon }\sigma-\text{bond at right angle}\\(d)\;\text{a plane perpendicular to the molecular plane which contains the carbon-carbon }\sigma-bond\end{array}$
