The first stable product of photosynthesis is glucose.
Photosynthesis is the process by which plants use sunlight, carbon dioxide, and water to produce glucose, which is a type of sugar that plants use as a source of energy. During the process of photosynthesis, light energy is used to convert carbon dioxide and water into glucose and oxygen. Glucose is considered the first stable product of photosynthesis because it is the first molecule produced that is able to be stored and used by the plant for energy.
Starch, fructose, and sucrose are all types of sugars that can be produced from glucose, but they are not the first stable product of photosynthesis. Glucose is the primary molecule produced during photosynthesis, and it is then converted into other forms of sugar for storage or transport within the plant.