Answer: The correct answer is Option b.
Step-by-step explanation:
Water is the compound which is formed by the covalent bonding of hydrogen and oxygen atoms. The chemical formula for this compound is

Self-ionization of water is defined as the process in which 2 water molecules react together to produce hydroxide ion and hydronium ion.
The equation for the self ionization of water molecule follows:

By Stoichiometry of the reaction:
2 moles of water molecules react together to produce 1 mole of hydronium ion and 1 mole of hydroxide ion.
Hence, the correct answer is Option b.