When potassium oxide (K2O) reacts with water (H2O), it produces potassium hydroxide (KOH):

• Chemical equation: K2O + H2O → 2KOH
• The reaction produces a hydroxide compound because the potassium ion balances the hydroxide ion and the solution is alkaline because of the high level of hydroxide ions, which gives it a high pH. Therefore, the correct answer is option D