B) is reduced.
Explanation:
Oxidation:
Oxidation involve the removal of electrons and oxidation state of atom of an element is increased.
Reduction:
Reduction involve the gain of electron and oxidation number is decreased.
Consider the following reactions.
4KI + 2CuCl₂  →  2CuI  + I₂  + 4KCl
the oxidation state of copper is changed from +2 to +1 so copper get reduced and it is oxidizing agent.
CO + H₂O  →  CO₂ + H₂
the oxidation state of carbon is +2 on reactant  side and on product side it becomes  +4 so carbon get oxidized and it is reducing gent.
Oxidizing agents:
Oxidizing agents oxidize the other elements and itself gets reduced.
Reducing agents:
Reducing agents reduced the other element are it self gets oxidized.