Why Is the Conversion of CO₂ to a 6-Carbon Sugar

Multiple Choice

Why is the conversion of CO₂ to a 6-carbon sugar so energetically expensive?

A) CO₂ is the most highly reduced and least energetic form in which carbon can occur.
B) CO₂ is very unstable.
C) CO₂ is the most highly oxidized and least energetic form in which carbon can occur.
D) CO₂ is the most highly oxidized and most energetic form in which carbon can occur.
E) CO₂ is highly unstable and only moderately energetic which makes the process more expensive energetically.