AP BIOLOGY

Detailed explanation-1: -The inner membrane in mitochondria is folded into cristae. The inner membrane in the chloroplast forms flattened sacs called thylakoids.

Detailed explanation-2: -Thylakoids of land plants have a bipartite structure, consisting of cylindrical grana stacks, made of membranous discs piled one on top of the other, and stroma lamellae which are helically wound around the cylinders.

Detailed explanation-3: -So, the correc answer is ‘Stroma’.

Detailed explanation-4: -Like mitochondria, chloroplasts have outer and inner membranes, but within the space enclosed by a chloroplast’s inner membrane is a set of interconnected and stacked, fluid-filled membrane sacs called thylakoids (Figure 2).