Answer: E. reforestation
Explanation:
Reforestation is a process of planting trees in an area so as to conserve the land as future forest. According to the given situation, reforestation is the practice which can be used by the biologists to grow nitrogen fixing plants in an area so as to increase the nutrient concentration of the soil which have been depleted.
Photosynthesis, how plants survive. Sunlight is absorbed.
Producer primary consumer secondary consumer tertiary consumer decomposer
Increase in temperature. I am not exactly sure what you're looking for but basically water vapour in the air has to do with evaporation of water from the surroundings so it will definitely have to do with the increase in global temperatures brought by global warming