Answer: D.
Explanation: The amount of light available is a crucial factor that affects a plant's rate of photosynthesis. Light energy is essential for the process of photosynthesis, during which plants convert light energy into chemical energy to fuel their growth and metabolism. Therefore, the strength or intensity of light directly influences the rate at which photosynthesis occurs in plants. Higher light levels generally lead to increased photosynthesis, while low light levels can limit the process.
On the other hand, options A, B, and C are not directly related to photosynthesis. The amount of wind, day of the week, and size of flower petals do not play significant roles in the process of photosynthesis in plants.