useless trivia: What Word Means: Reird?

Questions

australia is the richest source of mineral ---------- in the world?

because of a large orbital eccentricity, ---------- was closer to the sun than neptune between january 1979 and march 1999?

because of heavy---------- , julius caesar banned all wheeled vehicles from rome during daylight hours?

because of heavy traffic congestion, julius caesar banned all ---------- from rome during daylight hours?

because of heavy traffic congestion, julius caesar banned all wheeled vehicles from rome during----------?