Most of the enzymes of the calvin cycle also function in other metabolic pathways. this should not be a surprising finding, because
a) metabolic reactions are catalyzed by enzymes that have multiple functions
b) there is a close relationship between carbohydrate synthesis and carbohydrate metabolism
c) the calvin cycle probably evolved at the same time as did glycolysis
d) the calvin cycle is nearly ubiquitous in cells, as are metabolic pathways

The correct answer is B) "there is a close relationship between carbohydrate synthesis and carbohydrate metabolism".

Explanation:

The Calvin cycle are a series of chemical reactions that occurs in plant's stroma, and allow the convert carbon dioxide and other compounds into glucose in the absence of light. Most of the enzymes that function in Calvin cycle function as well in metabolic pathways,  because there is a close relationship between carbohydrate synthesis and carbohydrate metabolism. Particularly, gluconeogenesis and the pentose phosphate pathway have equivalent enzymes that those found in the Calvin cycle.