Describe the process of photosynthesis.

Photosynthesis is the fundamental process through which plants, algae, and some bacteria convert light energy into chemical energy. This occurs primarily in the chloroplasts of plant cells, where chlorophyll captures sunlight.

During photosynthesis, carbon dioxide from the air and water absorbed by the plant roots are transformed into glucose and oxygen through a series of chemical reactions. The chemical energy stored in glucose can later be used by the plant for growth and metabolism, making option A the most accurate description of photosynthesis.

The other options do not capture the essence of photosynthesis: absorbing nutrients from the soil pertains to plant nutrition rather than energy conversion; transporting water through plant tissues relates more to the process of transpiration and nutrient delivery; and regulating carbon dioxide in ecosystems is an aspect of the broader impact of photosynthesis on planetary health but does not define the process itself. Thus, the correct choice highlights the key function of photosynthesis in converting sunlight into a usable form of energy for plants.