Soil, in which nearly all our food grows, is a living resource that takes years to form. Yet it can vanish in minutes. Each year 75 billion tonnes of fertile soil is lost to erosion. That is alarming — and not just for food producers. Soil can trap huge quantities of carbon dioxide in the form of organic carbon and prevent it from escaping into the atmosphere.

Question: On the basis of the above passage, the following assumptions have been made:
1. Large-scale soil erosion is a major reason for widespread food insecurity in the world.
2. Soil erosion is mainly anthropogenic.
3. Sustainable management of soils helps in combating climate change.

Which of the above assumptions is/are valid?

The correct option is 3 only.

Let us analyze each of the given assumptions based strictly on the provided passage:

Assumption 1: "Large-scale soil erosion is a major reason for widespread food insecurity in the world."
The passage states that soil takes years to form, vanishes in minutes, and that 75 billion tonnes of fertile soil is lost to erosion annually, which is "alarming — and not just for food producers." While it highlights a threat to food production, the passage does not state or logically imply that soil erosion is currently a "major reason for widespread food insecurity in the world." This makes Assumption 1 invalid based strictly on the text.

Assumption 2: "Soil erosion is mainly anthropogenic."
"Anthropogenic" means caused or influenced by humans. The passage describes the rate of soil loss (75 billion tonnes per year) and its consequences, but it does not discuss the causes of soil erosion (whether they are natural or human-induced). Therefore, we cannot assume from the passage that soil erosion is mainly anthropogenic, making Assumption 2 invalid.

Assumption 3: "Sustainable management of soils helps in combating climate change."
The passage states: "Soil can trap huge quantities of carbon dioxide in the form of organic carbon and prevent it from escaping into the atmosphere." Preventing carbon dioxide (a major greenhouse gas) from escaping into the atmosphere is a key mechanism for combating climate change. Therefore, managing soils sustainably to prevent erosion and preserve their carbon-trapping capacity directly helps in combating climate change. This makes Assumption 3 a valid assumption based on the passage.

Hence, only assumption 3 is valid.