Organic peroxides are assigned to which ADR class, and why does the basic-module driver treat them as a distinct fire and decomposition risk?

1. Class 5.2; they can decompose, sometimes violently, and may require temperature control
2. Class 3; they are ordinary flammable liquids with no extra rules
3. Class 1; they are always treated as explosives on the basic paper
4. Class 8; they are only corrosive and never flammable