Concept:Dehydration of ethanol involves loss of a water molecule from the alcohol molecule.Explanation:When ethanol is dehydrated, it produces ethene and water.The reaction is:C2H5OH→C2H4+H2OIn this process, atoms are removed from adjacent carbon atoms.A double bond forms between the two carbon atoms.This loss of atoms from a molecule without substitution is classified as an elimination reaction.Answer:B. an elimination reaction