acids are species that release H⁺ ions/protons. Hydrogen ions are also called protons since they have no electron and only proton.
When hydrogen ions are added to water - H₂O, oygen tends to donate one of its lone pairs to H⁺ which is electron deficient in the form of a dative bond.
thereby making a hydronium ion.
written as H₃O⁺.
when neutral H₂O donates an electron pair to H⁺, the overall charge of the ion becomes positive.
answer is B. hydronium ions