Read the passage and answer the questions given below it.
When a field gives a good crop, the farmer, the rain and the seed usually share the credit. Hardly anyone thinks of the earthworm. It lives out of sight, it is slimy, and most people meet it only on a wet path after a storm. Yet much of the work that keeps soil alive goes on in its dark tunnels.
An earthworm eats its way through the ground, swallowing soil along with bits of dead leaves and roots. What comes out at the other end, called a cast, is richer in plant food than the soil around it. Its burrows matter just as much. They let air reach the roots, and they help rainwater soak in instead of running off the surface.
Charles Darwin watched these animals on and off for about forty years. His last book, published in 1881, was about earthworms. He estimated how fast their casts piled up, and he showed that stones and even old ruins left on the ground slowly sink under it, buried a little at a time by the soil the worms bring up.
Today many gardeners keep worms to turn kitchen waste into vermicompost. On farms, though, the story often runs the other way. Repeated deep ploughing tears up their burrows, and some pesticides kill them or bring their numbers down. The loss does not show at once. It shows later, in soil that packs hard and lets water stand on top after rain.
According to the passage, the burrows of earthworms
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → allow air and water to get down into the soil.
The second paragraph says what the burrows do.
- The burrows “let air reach the roots”.
- They also “help rainwater soak in instead of running off the surface”.
Why the Other Options are Incorrect?
Option 1: make the ground firmer, so that plant roots can grip it better. — Incorrect. Contradicted: The passage says that when worms are lost, the soil “packs hard”. So the burrows keep the ground loose, not firm.
Option 2: carry the plant food in the casts down to the deepest roots. — Incorrect. Wrong link: The passage links plant food with the casts and air and water with the burrows. It never says the burrows carry food anywhere.
Option 4: are destroyed mainly by the pesticides sprayed on farms. — Incorrect. Wrong reason: In the passage it is “deep ploughing” that tears up the burrows. Pesticides kill the worms themselves.