Answer:
The most appropriate answer would be A - The dark reactions would stop happening.
Light-independent or dark reaction or Calvin cycle is a part of photosynthesis in which products of light-dependent reaction (ATP and NADPH) are used to fix carbon from carbon dioxide into glucose.
It takes around 9 molecules of ATP and 6 molecules of NADPH in order to produce 1 molecule of glucose.
So, if ATP production would be stopped in a plant then dark reaction would also stop happening.