Final answer:
In pure water, the main component is the water molecule, H₂O, but it also contains very low concentrations of hydronium ions (H₃O⁺) and hydroxide ions (OH⁻) due to self-ionization, making the correct answers H₂O and more than one response is correct.
Step-by-step explanation:
The components present in pure water can be derived from its self-ionization reaction, which is represented by the equation 2H₂O → H₃O⁺ + OH⁻. This reaction shows that pure water partially dissociates into hydronium ions (H₃O⁺) and hydroxide ions (OH⁻). However, the predominant species in pure water is the water molecule itself, represented as H₂O. Both H₃O⁺ and OH⁻ are present in very low concentrations, maintaining a neutral pH of 7 at 25 °C, where their concentrations are equal at 1.0 x 10⁻⁷ M. Therefore, the correct answers are H₂O and, because of the self-ionization reaction, more than one response is correct.