"If rainforests and tropical forests are the lungs of the Earth, then surely wetlands function as its kidneys." Which one of the following functions of wetlands best reflects the above statements?

Answer: (d) Aquatic plants absorb heavy metals and excess nutrients.

Kidneys remove waste from blood; aquatic plants absorb heavy metals and excess nutrients from water — the same job.

The idea

The question is about an analogy. Lungs exchange gases. Kidneys filter blood and remove waste. So pick the wetland function that is filtering.

Dirty water flows into a wetland → Plants slow it down → Mud and silt settle → Plants and microbes take up nitrates, phosphates and metals → Cleaner water flows out

Why the others are wrong

(b) That is wetlands as a food base — more like a “supermarket”.

The trap

All four statements are true of wetlands. Only (d) matches the analogy.

Also know

The East Kolkata Wetlands, a Ramsar site, clean the city’s sewage through fish ponds and farms at almost no cost. Engineers copy the idea in “constructed wetlands”. Other wetland services: soaking up floods like a sponge, recharging groundwater and storing carbon in peat.