Explanation:
One double bond and one chiral center, so total stereoisomers are 4.

\[\begin{array}{*{20}{l}}
{{\rm{cis}}\,{\rm{and}}\,{\rm{d}} - {\rm{or}}{\mkern 1mu} ({\rm{ + }}){\mkern 1mu} {\rm{form}}}\\
{{\rm{cis}}\,{\rm{and}}\,{\rm{l}} - {\rm{or}}{\mkern 1mu} ( - ){\mkern 1mu} {\rm{form}}}\\
{{\rm{Trans}}\,{\rm{and}}{\mkern 1mu} {\mkern 1mu}\, {\rm{d}}\,{\rm{or}}{\mkern 1mu} ({\rm{ + }}){\mkern 1mu} {\rm{form}}}\\
{{\rm{Trans}}\,{\rm{and}}{\mkern 1mu} {\mkern 1mu}\, {\rm{l}}\,{\rm{or}}{\mkern 1mu} ( - ){\mkern 1mu} {\rm{form}}}
\end{array}\]