In the context of India, which of the following is/are considered to be practice(s) of eco-friendly agriculture ? 1. Crop diversification 2. Legume intensification 3. Tensiometer use 4. Vertical farming Select the correct answer using the code given below :

Option (D) is correct because all four techniques promote sustainability: crop diversification and legume intensification enhance soil fertility and biodiversity, while tensiometers and vertical farming optimize water and land use efficiency. Option (a) is the most tempting distractor as candidates often exclude vertical farming assuming it is not a widespread "practice" in India, yet it is an inherently eco-friendly method that reduces pesticide and water consumption. The core concept tested is the identification of sustainable agricultural practices that conserve natural resources and reduce chemical dependency.