Practice question What does the hazard identification number "263" stand for? Toxic gas, flammableFlammable liquid, toxicCorrosive gas, toxicOxidizing gas, flammable Answer: A — Toxic gas, flammable The correct answer is shown above. Try the full quiz for additional practice. Practice more: ADR Core Module Practice Questions - ADR Dangerous Goods Driver Training Certificate - Core Module (Europe) Exam →