What is Vulcanization?

Question

$\begin{array}{1 1} \text{(a) Vulcanization is a chemical process in which the rubber is heated with benzene, accelerator and activator at 140–160°C.} \\ \text{(b)Vulcanization is a chemical process in which the rubber is heated with nitrogen, accelerator and activator at 140–160°C.} \\ \text{(c) Vulcanization is a chemical process in which the rubber is heated with sulphur, accelerator and activator at 140–160°C.} \\ \text{(d) Vulcanization is a chemical process in which the rubber is heated with zinc at 140–160°C.}\end{array}$