The correct answer is: D. water (steam).
Ethene is a hydrocarbon with the chemical formula $C_2H_4$. It is a colorless, flammable gas that is used in the production of plastics, rubber, and other chemicals.
Water (steam) is a compound with the chemical formula $H_2O$. It is a colorless, odorless, tasteless liquid that is essential for life.
When ethene is reacted with water (steam) in the presence of phosphoric acid, a chemical reaction called hydration occurs. In this reaction, the hydrogen atoms from the water molecule are bonded to the carbon atoms in the ethene molecule, and the oxygen atom from the water molecule is bonded to the carbon atoms in the ethene molecule. This reaction produces ethanol, a compound with the chemical formula $C_2H_5OH$.
Ethanol is a colorless, flammable liquid that is used as a fuel, a solvent, and a preservative. It is also the main ingredient in alcoholic beverages.
The other options are incorrect because they do not react with ethene to produce ethanol.
- Hydrogen is a gas that is used in the production of ammonia, methanol, and other chemicals. It does not react with ethene to produce ethanol.
- Potassium dichromate is a salt that is used as a mordant in dyeing and as an oxidizing agent in organic chemistry. It does not react with ethene to produce ethanol.
- Oxygen is a gas that is essential for life. It does not react with ethene to produce ethanol.