(c)
1, 2-dihalogen ($vicinal$) derivatives of the alkanes on reaction with zinc dust and methanol produces alkenes by loss of two halogen atoms (dehalogenation).
$CH_{3} - CH - CH_{2} + Zn\overset{\frac{Alcohol}{\mathrm{\Delta}}}{\rightarrow}CH_{3}CH = CH_{2}$
| | propylene
$Br\ \ \ \ \ \ \ Br$
1,2-dibromopropane