Which of the following combinations represent renewable natural resources ?

Concept

A natural resource is called renewable when natural processes replenish its stock on a human timescale — reproduction, the water cycle, photosynthesis, soil formation, or a physical force that acts continuously. It is called non-renewable when it was formed over geological time and is drawn down far faster than it re-forms. A combination question adds one further rule: the label applies to a set only if every member of that set satisfies the definition, so a single non-renewable member disqualifies the whole combination.

Application

Classify every resource named across the four combinations against that definition:

Now apply the "every member" rule. The combination "Fishes, fertile soil and fresh water" is the only one in which all three members are replenished on a human timescale — fish stocks by spawning, soil by weathering and organic-matter recycling, and fresh water by the hydrological cycle. It is therefore the combination of renewable natural resources.

Cross-check

• "Fertile soil, fresh water and natural gas" carries two renewable members, but natural gas is a fossil fuel formed over millions of years, so the set as a whole is not renewable.

• "Clean air, phosphates and biological diversity" pairs two renewable members with phosphate rock, a mined mineral deposit that does not re-form on a human timescale.

• "Oil, forests and tides" is the usual trap: forests regrow and tidal energy is effectively inexhaustible, yet crude oil is a fossil fuel — and one non-renewable member is enough to disqualify the set.

• A final caution: renewable does not mean unlimited. Fish stocks, soil fertility and fresh water can all be exhausted if they are used faster than they regenerate; renewability describes the replenishment process, not an infinite supply.