Which statement about vulcanisation of natural rubber with sulfur is correct?

1. ASulfur forms cross-links between chains at reactive sites near the C=C bonds, making the rubber harder and extending its useful temperature range
2. BSulfur converts the cis double bonds of rubber into trans double bonds
3. CSulfur cleaves the chains, which lowers the molar mass and increases elasticity without limit
4. DSulfur removes all the C=C bonds by hydrogenation and gives linear saturated chains without cross-links