Answer the following question given this paragraph: 

As Melvin Calvin discovered, carbon fixation is the first step of a cycle. Like an electron transport chain, the Calvin Cycle, shown in Figure below , transfers energy in small, controlled steps. Each step pushes molecules uphill in terms of energy content. Recall that in the electron transfer chain, excited electrons lose energy to NADPH and ATP. In the Calvin Cycle, NADPH and ATP formed in the light reactions lose their stored chemical energy to build glucose.


Q: Carbon fixation is the first step of what cycle involving light reactions?

 Choices:

- sun cycle

- life cycle

- water cycle

- calvin cycle

A:
calvin cycle
