How should old oil be disposed?

Answer: C — Correctly at the local authority site

Old oil should not be disposed of in household waste as this can contaminate the environment and harm wildlife. It should also not be poured down the drain as it can clog and damage sewage systems. Reusing for lubrication is not recommended as recycled oil may contain harmful contaminants. Therefore, the best and most responsible option is to dispose of old oil correctly at a local authority site.