Question

Which represents the self ionization of water at 25 degrees Celsius

Answer 1

Auto-ionization of water: 
HOH(l) ↔ H⁺(aq) + OH⁻(aq) 

You might also see: 
2HOH ↔ H₃O⁺ + OH⁻ .......... or ............ H₂O + H₂O ↔ H₃O⁺ + OH⁻