Achloroplast is releasing large amounts of oxygen. what does this tell you about what other processes are going on inside the chloroplast

Chloroplasts are organelles within plant cells that contain chlorophyll and are responsible for carrying out photosynthesis. This process which is utilised by plants to manufacture food, requires carbon dioxide and water which is then converted into glucose and oxygen. Therefore, the release of oxygen tells us that photosynthesis is occurring inside the chloroplast. 

The right answer is c.sandstone.