Correct Option (B)
Assumption 3 is valid. The passage explicitly states that "Soil can trap huge quantities of carbon dioxide in the form of organic carbon and prevent it from escaping into the atmosphere." This directly implies that maintaining healthy soil through sustainable management practices contributes to carbon sequestration, thereby assisting in the mitigation of climate change.
Incorrect Options:
Assumption 1 is not valid. While the passage highlights the importance of soil for food production ("nearly all our food grows") and mentions that soil loss is "alarming and not just for food producers," it does not provide sufficient information to conclude that large-scale soil erosion is a major reason for widespread food insecurity globally. The passage indicates a concern for food producers but does not quantify the impact on overall food security or identify it as a primary cause of insecurity.
Assumption 2 is not valid. The passage states that "Each year 75 billion tonnes of fertile soil is lost to erosion" but does not specify the causes of this erosion. There is no information provided within the passage to support the assumption that soil erosion is mainly anthropogenic (primarily caused by human activities). The passage remains neutral on the origins of the erosion mentioned.