The correct answer is: B. An oxidising agent.
Carbon dioxide is an oxidising agent because it can accept electrons from other substances. This is because carbon dioxide has a high electronegativity, which means that it is able to attract electrons to itself. When carbon dioxide accepts electrons from other substances, it is reduced and the other substance is oxidised.
A reducing agent is a substance that can donate electrons to other substances. This is because reducing agents have a low electronegativity, which means that they are able to give electrons away. When a reducing agent donates electrons to another substance, it is oxidised and the other substance is reduced.
A dehydrating agent is a substance that can remove water from other substances. This is because dehydrating agents have a strong affinity for water molecules. When a dehydrating agent comes into contact with water, it will absorb the water and become hydrated.
A bleaching agent is a substance that can remove colour from other substances. This is because bleaching agents typically contain oxygen, which can react with the pigments in the substance to bleach them.
In conclusion, carbon dioxide is an oxidising agent because it can accept electrons from other substances. This is because carbon dioxide has a high electronegativity, which means that it is able to attract electrons to itself.