The hydrogenation of butene involves the addition of hydrogen gas to the double bond of butene molecule. This reaction is a type of addition reaction, where two reactants combine to form a single product.
The product of the hydrogenation of butene is butane. This is because the addition of hydrogen to the double bond of butene saturates the carbon atoms, and forms a single bond between them, resulting in a straight-chain alkane.
Therefore, the correct answer is "butane".