Stroma of chloroplasts carries the fixation of

Explanation

The stroma of chloroplasts is where the Calvin cycle occurs, which is responsible for fixing carbon dioxide (CO2) into organic molecules like glucose. This process uses ATP and NADPH generated during the light-dependent reactions. In contrast, nitrogen fixation, crucial for converting atmospheric nitrogen (N2) into a form usable by plants, is performed by certain bacteria. Oxygen (O2) is a byproduct, not a fixed compound in photosynthesis, and ammonia (NH3) is involved in processes outside the chloroplast.