The correct answer is A. Chloroplast.
Chloroplasts are organelles found in plant cells and some algae. They are responsible for photosynthesis, the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
Mitochondria are organelles found in all eukaryotic cells. They are responsible for cellular respiration, the process by which cells convert glucose into energy.
Golgi bodies are organelles found in all eukaryotic cells. They are responsible for packaging and exporting proteins and other molecules.
Endoplasmic reticulum is a network of tubules and sacs found in all eukaryotic cells. It is involved in the synthesis of proteins and lipids, and in the transport of molecules within the cell.
In conclusion, chloroplasts are the organelles of a cell that are involved in photosynthesis.