The correct answer is option 1: Chloroplast. Chloroplasts are membrane-bound organelles found in the cells of plants and algae. They are responsible for carrying out photosynthesis, the process by which plants convert sunlight into chemical energy in the form of glucose. Within the chloroplasts, there are structures called thylakoids which contain chlorophyll, a pigment that absorbs sunlight. The chlorophyll molecules use the energy from light to convert carbon dioxide and water into glucose and oxygen. This glucose is used by the plant as a source of energy for growth and metabolism. Therefore, the presence of chloroplasts in plant cells is crucial for photosynthesis to occur and for plants to produce their own food.