Which is the internal membrane of the chloroplasts that is organized into flattened membranous sacs ?

THYLAKOIDS the term used to describe the cholorophlasts internal membrane where it is organized into flattened membranous sacs.

The thylakoids are arranged in orderly stacks called grana that contain energy-transducing machinery.

The space inside the thylakoid sac is called lumen and the space outside the thylakoid sac but still within the chloroplast is called stroma.

The right answer is c.sandstone.