In the Calvin cycle, CO2 is combined with _____.
a) a 2-carbon compound to form a 3-carbon compound
b) a 5-carbon compound to form an unstable 6-carbon compound, which decomposes into two 3-carbon compounds
c) a 7-carbon compound to form two 4-carbon compounds
d) a 5-carbon compound to form a stable 6-carbon compound that can be converted directly to glucose
e) two 2-carbon compounds to form a 5-carbon compound
