The correct option is D Chloroplasts
Thylakoid is a flattened disc-like sac found inside a chloroplast which is the site of photosynthesis, in plants and algae. Thylakoids are membrane-bound structures embedded in the chloroplast stroma. A stack of thylakoids is called a granum and resembles a stack of coins.Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. In the thylakoid membrane, there are two photosystems (I and II). Hence option A is correct.