Final answer:
Option C, that more NADPH would be produced during the cyclic electron pathway, would not be true if plants could only perform cyclic photophosphorylation, as this process generates ATP without producing NADPH or oxygen.
Step-by-step explanation:
If plants were only able to undergo the cyclic pathway of photosynthesis, Option C: More NADPH would be produced during the cyclic electron pathway would NOT be true. During cyclic photophosphorylation, the high energy electrons from Photosystem I (PSI) are passed through the electron transport system (ETS) and ultimately return to PSI without the production of NADPH. Instead, this process primarily generates ATP to meet the cell's immediate energy needs, especially when the demand for ATP is higher than that for NADPH. In contrast, noncyclic photophosphorylation, which also involves Photosystem II (PSII), leads to the production of both ATP and NADPH, essential for the Calvin cycle to synthesize carbohydrates such as glucose. Moreover, it is only during noncyclic photophosphorylation that oxygen is produced as a by-product of splitting water molecules (oxygenic photosynthesis).
Therefore, when plants rely solely on cyclic photophosphorylation, they are unable to produce NADPH or oxygen, carbohydrates are synthesized in reduced quantities since less ATP and no NADPH are generated in comparison to noncyclic photophosphorylation, and the sole focus remains on ATP production to satisfy immediate energy requirements of the plant.