In photosynthesis, the carbon in co2 is being to form glucose.

The answer is reduced. In a redox reaction, the reduction is the gaining of a proton in a reaction or losing of electrons while oxidation is the gaining of electrons or losing of a proton. In other words, it is the transformation in the oxidation number between the reactants and the products. Carbon dioxide in photosynthesis gains protons (hydrogen) from water molecules hence it is reduced. See reaction below;

6CO2(g)+24H++24e−→C6H12O6(aq)+6H2O(l)

reduced


Justification:


1) Reduction is the reduction of the oxidation state, which occurs by gain of electrons.


2) Oxidation is the increase of the oxidation state, which occurs by the loss of electrons.


3) In the photosynthesis, CO₂ reacts with water (in the presence of light) to form glucose and oxygen according to this equation:


CO₂ + H₂O ---> C₆H₁₂O₆ + 6 O₂

4) The oxidation number of C in CO₂ is +4, while the oxidation number of C in C₆H₂O₆ is 0. So, the oxidation number of C has been reduced from +4 to 0, which is what is defined by reduction.