In which part of the chloroplast does the Calvin cycle take place?

The Calvin cycle takes place in the stroma of the chloroplast, making this the correct answer. The stroma is the fluid-filled space surrounding the thylakoid membranes and is rich in enzymes and other important molecules necessary for the process of carbon fixation. Here, ATP and NADPH generated from the light-dependent reactions (which occur in the thylakoid membranes) are utilized to convert carbon dioxide into glucose.

The thylakoid membrane is specifically involved in the light-dependent reactions, where light energy is converted into chemical energy. Chlorophyll molecules are embedded within the thylakoid membranes and are crucial for capturing light energy. Granum refers to stacks of thylakoids within the chloroplast. While all these components are integral to the overall process of photosynthesis, the Calvin cycle uniquely occurs in the stroma.