Which of the following words is closest in meaning to “Vulcanize”?

Vulcanize means to toughen rubber by treating it with sulphur.

• Correct answer - to toughen rubber by treating it with sulphur: it has the same meaning as Vulcanize.
• erupt: to burst out - wrong, it does not mean the same as Vulcanize.
• roll hot metal into a rubber sheet: a nonsensical process of rolling metal into rubber - wrong, it does not mean the same as Vulcanize.
• to interlink: to connect together - wrong, it does not mean the same as Vulcanize.