Which of the Following Could Describe the Relationship Between the Cyanobacterium

Which of the following could describe the relationship between the cyanobacterium Nostoc and E.coli related to the carbon cycle?

A) Nostoc produces carbohydrates from lithotrophy, and E. coli breaks down the carbohydrates to generate CO₂.
B) Nostoc produces carbohydrates from phototrophy, and E. coli breaks down the carbohydrates to generate CO₂.
C) Nostoc produces CO₂ that E. coli turns into carbohydrates.
D) E. coli produces carbohydrates that Nostoc uses as energy to produce more carbohydrates.