The correct option is 1, 2, and 3 because mycorrhizal associations enhance plant growth and resilience by extending the root system's absorptive capacity, enabling plants to access water and nutrients more effectively, thus improving drought resistance. Additionally, mycorrhizae can help plants adapt to challenging soil conditions, such as extreme pH levels, and they contribute to disease resistance by enhancing plant health and resilience through their interactions with beneficial soil microbes. These factors are crucial in rehabilitating degraded ecosystems, aiding in soil health restoration and promoting sustainable agriculture, aligning with the objectives of environmental conservation and resource management outlined in UPSC syllabus.