Biodiversity forms the basis for human existence in the following ways: 1) Soil formation 2) Prevention of soil erosion 3) Recycling of waste 4) Pollination of crops Select the correct answer using the codes given below:

The answer is D. All four statements describe ways biodiversity supports human life, so the only option that includes all four is D.

The core concept is ecosystem services, the benefits humans get from functioning ecosystems. These are usually grouped as provisioning, regulating, supporting and cultural services. Soil formation and recycling of waste (nutrient cycling by decomposers) are supporting services. Prevention of soil erosion, through plant roots and ground cover, and pollination of crops by insects and other animals are regulating and supporting services. Mains GS-3 often asks about ecosystem services in the context of food security and the economic valuation of biodiversity.

• Option A leaves out pollination of crops, which is a direct link between pollinator diversity and food production.
• Option B leaves out soil formation, which depends on decomposers, microorganisms and soil fauna.
• Option C covers only two of the four and drops erosion control and waste recycling.

Trap: Aspirants tend to pick A or B because they treat one of the statements as a weaker or more indirect benefit. Each of the four is a standard ecosystem service listed in NCERT Class XI and XII Biology, so the safe choice is the option that includes all of them.