Final answer:
The correct summary for photosynthesis is CO₂ + H₂O → O₂ + sugars, where, with sunlight, carbon dioxide and water are converted into glucose and oxygen. The full reaction is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, indicating this process as essential for producing energy-rich sugars.
Step-by-step explanation:
The overall process of photosynthesis is correctly summarized by option 4: CO₂ + H₂O → O₂ + sugars. This complex multi-step reaction requires sunlight, carbon dioxide, and water to produce oxygen and carbohydrates like glucose. The detailed chemical reaction for photosynthesis can be represented by the equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, where the energy from sunlight is used to convert six molecules of carbon dioxide and six molecules of water into one molecule of glucose and six molecules of oxygen, making glucose and other simple carbohydrates which are high in energy and essential for life.