The structures that are formed by stacking of organised flattened membranous sacs in the chloroplasts are (a) stroma lamellae (b) stroma (c) cristae (d) grana.
Option D is correct answer. A chloroplast is a vesicle, bound by an envelope of two unit membranes and filled with a fluid matrix called stroma. The lamellae, after separation from the inner membrane, usually take the form of closed, flattened, ovoid sacs, the thylakoids, which lie closely packed in piles, the grana.
