The calvin cycle and the krebs cycle are referred to as cycles of chemical reactions because they
occur inside organelles.
start over continually.
are part of the carbon cycle.
allow energy to flow in ecosystems.

start over continually.

The Calvin cycle of photosynthesis begins when the carbon dioxide is attached to RuBP (A). The Calvin cycle refers to the light-independent reactions in photosynthesis. The Calvin cycle occurs in three steps.The Calvin cycle is indirectly dependent on the light since the energy carriers, for example, ATP, are products of light-dependent reactions. The second step is that the CO2 is fixed from an inorganic molecule to an organic molecule. In the third and final stage, RuBP is regenerated. This enables the system to prepare for more CO2 to be fixed. 

The answer is b. hope this !