Answer
$cis-2,3-dichlorobut-2-ene$ has a higher boiling point.
$trans-2,3-dichlorobut-2-ene$ has zero dipole moment.
Work Step by Step
$cis-2,3-dichlorobut-2-ene$ has a higher boiling point because it has dipole-dipole interactions, whereas $trans-2,3-dichlorobut-2-ene$ has zero dipole moment.