Which one of the following is not among the “three Rs”, a slogan for solid…

Concept. The “three Rs” is a fixed three-term slogan of the waste-management hierarchy. It names three actions, in descending order of priority, that keep material out of final disposal: cutting the amount of waste created at source, using an article again in the form it already has, and reprocessing discarded material into fresh raw material. Only these three terms belong to the slogan; every other “R” word used in waste literature sits outside it, in the longer hierarchies built on top of the slogan.

Application. Test each offered term against that fixed set of three:

• Reduce — cutting the quantity of waste generated at source. This is the first of the three terms.

• Reuse — using an article again in its existing form, without reprocessing. This is the second of the three terms.

• Recycle — reprocessing discarded material into fresh raw material for new goods. This is the third of the three terms.

• Recover — extracting residual value, chiefly energy, from waste that is no longer usable as material (waste-to-energy incineration, landfill-gas capture). This term does not belong to the three-term slogan.

Cross-check. The formal waste hierarchies that extend the slogan keep recovery as a separate, lower-priority step, which confirms it was never inside the three:

• The EU Waste Framework Directive sets five steps — prevention, preparing for re-use, recycling, other recovery, disposal — listing “other recovery” below recycling as a distinct stage.

• The 4R / 5R / 7R expansions exist precisely because words such as Recover, Refuse, Repair and Rethink had to be added to the original three.

Result. Among the four terms offered, the one that is not part of the “three Rs” is Recover.