Identify the overall change in the following set of reactions. 

1. Carbon dioxide $$\rightarrow$$ carbonic acid $$H_2CO_3$$. 

2. Ethanol (alcohol) → Ethanal (aldehyde)

3. Ethanal (aldehyde) → Ethanol (alcohol)

4. Sulphuric acid to sulphur trioxide $$SO_3$$. 

Choose the correct option which best describes these conversions.

A

oxidation, oxidation, reduction, reduction

B

hydration, oxidation, reduction, dehydration

C

reduction, dehydration, hydration, oxidation

D

reduction, reduction, oxidation, oxidation