Final answer:
The conversion of CH3CH3 to H2C=CH2 is an oxidation reaction.
Step-by-step explanation:
Oxidation is the process of gaining oxygen or losing hydrogen in a compound, while reduction is the process of gaining hydrogen or losing oxygen. In the given example, the conversion of CH3CH3 to H2C=CH2 involves the removal of two hydrogen atoms and the addition of a double bond. This means that hydrogen is lost, so it is an oxidation reaction.